Dissertations / Theses on the topic 'Dairy calves'

Twenty-eight Holstein and crossbred calves of both genders were used to evaluate the effect of milk replacer antibiotics on abundance of selected antibiotic resistance genes (ARG) in the feces. Calves were blocked by breed, gender, and birth order, and assigned to one of three treatments at birth. Treatments were control (containing no antibiotics in the milk replacer), subtherapeutic (neomycin sulfate and oxytetracycline hydrochloride each fed at 10 mg/calf/d), and therapeutic (no antibiotics in the milk replacer until d 36, then neomycin sulfate and oxytetracycline hydrochloride each fed at 1000 mg/calf/d for 14 d). Calves were fed milk replacer twice daily at 0600 h and 1800 h. Fecal and respiratory scores and rectal temperatures were recorded daily. Calves were weighed at birth and weaning to calculate average daily gain. Beginning at six weeks of age fecal grab samples were collected from heifers at 0600 h, 1400 h, 2000 h, and 2400 h for 7 d, while bull calves were placed in metabolism crates for collection of all feces and urine. DNA was extracted from feces, and ARG corresponding to the tetracyclines (tetC, tetG, tetO, tetW, and tetX), macrolides (ermB, ermF), and sulfonamides (sul1, sul2) classes of antibiotics along with the class I integron gene, intI1, were measured by quantitative polymerase chain reaction (qPCR). No tetC or intI was detected. There was no significant effect of antibiotic treatment on the absolute abundance (gene copies/ g wet manure) of any of the ARG except ermF, which was lower in the antibiotic-treated calf manure probably because host bacterial cells carrying ermF were not resistant to tetracycline or neomycin. All ARG except tetC and intI were detectable in feces from 6 weeks onwards, and tetW and tetG significantly increased with time (P < 0.10), even in control calves. Overall, the majority of ARG analyzed for were present in the feces of the calves regardless of exposure to dietary antibiotic. Feed antibiotics had little effect on the ARG monitored; other methods for reducing the ARG pool should also be investigated.<br>Master of Science

Submitted by Marco Antônio de Ramos Chagas (mchagas@ufv.br) on 2017-11-14T12:59:59Z No. of bitstreams: 1 texto completo.pdf: 3045284 bytes, checksum: 75fae3d40e3e0a912a8276323170df28 (MD5)<br>Made available in DSpace on 2017-11-14T12:59:59Z (GMT). No. of bitstreams: 1 texto completo.pdf: 3045284 bytes, checksum: 75fae3d40e3e0a912a8276323170df28 (MD5) Previous issue date: 2017-02-22<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>Ao nascimento, os bezerros exibem um trato gastrointestinal subdesenvolvido (TGI) cuja maturação é estritamente relacionada à colonização da microbiota. No entanto, pouco se sabe sobre os fatores que afetam o estabelecimento de comunidades de archaeas, bacterias e de fungos anaeróbicos no TGI dos bezerros, bem como as mudanças na estrutura e abundância desses grupos microbianos durante o período de transição da fase de pré-ruminante para verdadeiro ruminante. Para abordar essas lacunas no conhecimento, este trabalho empregou sequenciamento de próxima geração para caracterizar a microbiota do TGI de bezerros leiteiros mestiços (Holandês-Gir) durante o período pré-desmame. O primeiro estudo avaliou mudanças nas comunidades de archaeas metanogênicas, bacterias e fungos anaeróbicos no rúmen de bezerros leiteiros (n = 45) alimentados com duas dietas diferentes (M: somente leite cru (10% do peso vivo (PV)) e MC: leite cru (10% PV e concentrado ad libitum) e que foram abatidos aos 7, 28, 49, 63 dias de idade. No segundo estudo, caracterizamos as alterações nas comunidades bacterianas entre regiões GIT (rúmen, jejuno, ceco e cólon) de bezerros alimentados com MC (n = 17) que foram abatidos aos 7, 28, 49, 63 dias de idade. Os resultados do primeiro estudo revelaram que as comunidades de archaeas metanogênicas, bacterias e fungos coexistem no rúmen desde a primeira semana de vida, mas são afetadas diferentemente pela dieta e idade. A inclusão de concentrado na dieta de bezerros afetou significativamente a comunidade bacteriana do rúmen: observou-se um aumento na abundância de gêneros relacionados, direta e indiretamente, à degradação de amido (i.e. Megasphaera, Sharpea e Succinivribrio) e um decréscimo acentuado na abundancia de gêneros (i.e. Lactobacillus, Bacteroides e Parabacteroides) relacionados com a degradação de nutrientes do leite. Alterações na comunidade bacteriana, indiretamente afetaram a comunidade de metanogênicas: fermentação de carboidratos não fibrosos alterou padrões de fermentação (acetato:propionato) e disponibilidade de hidrogênio que por sua vez, favoreceu a colonização de Methanosphaera em vez de Methanobrevibacter. Na comunidade de fungos anaeróbicos, a abundância do genêro Caecomyces e família Neocallimastigaceae não variou significativamente com a dieta ou idade, provavelmente devido à alta variação inter-animal e baixo teor de fibra de concentrado usado em nosso estudo. In suma, este estudo mostrou que a manipulação da microbiota no rúmen em desenvolvimento é possível através da intervenção dietética. Nossos resultados podem ser úteis na elaboração de estratégias para promover a colonização de comunidades-alvo (isto é, produtores de butirato e utilizadoras de lactato) que estão ligadas ao desenvolvimento de papilas e equilíbrio do pH ruminal. Em relação ao segundo estudo, as comunidades bacterianas diferem qualitativa e quantitativamente entre os compartimentos (rúmen, jejuno, cécum e colón) do trato gastrointestinal e também respondem diferentemente ao avanço da idade que inclui a substituição progressiva da dieta líquida para a dieta sólida (i.e. aumento do consumo de concentrado). No rúmen, a comunidade bacteriana foi composta em sua maioria pelos gêneros Prevotella, Butyrivibrio e Ruminococcus cuja abundância aumentou proporcionalmente com a idade devido a maior disponibilidade de carboidratos não fibrosos no rúmen. No jejuno, o gênero Lactobacillus foi abundante desde a primeira semana de vida, mas sua dominância foi substituída por membros da família Clostridiaceae em bezerros mais velhos. As comunidades do ceco e do cólon foram compostas pelos gêneros Blautia, Paraprevotella, Prevotella Phascolarctobacterium and Succiniclasticum cuja abundância aumentou com a idade. Em resumo, nossos resultados mostraram que, embora comunidades bacterianas coexistam em regiões distintas do TGI, uma análise mais detalhada da estrutura, abundância e dinâmica dessas comunidades revela uma marcante segregação e sucessão ecológica no TGI de bezerros. Nosso estudo acrescenta novos insights sobre a colonização bacteriana no TGI de pré-ruminantes que podem servir como base para formulação de estratégias para promover a colonização de comunidades-alvo (i.e. bactérias probióticas) para melhorar a saúde e desempenho de bezerros leiteiros no período pré-desmame.<br>At birth, calves display an underdeveloped gastrointestinal tract (GIT) whose maturation is strictly related to microbiota colonization. However, little is known about the factors that affect the establishment of archaeal, bacterial and fungal communities in the GIT of calves, as well as the changes in their structure and abundance during calf development into a functional ruminant. To address these gaps in knowledge, this work employed next-generation sequencing to characterize the GIT microbiota of Holstein- Gyr crossbred dairy calves across pre-weaning development. The first study aimed to assess changes on the rumen archaeal, bacterial and fungal communities of crossbred dairy calves (n=45) across pre-weaning development (7, 28, 49, 63 days) on two different diets (M: only raw milk at 10% of body weight at birth (BW) and MC: raw milk (10% BW) plus starter concentrate ad libitum). In the second study, we characterized changes in the bacterial communities across GIT regions (rumen, jejunum, cecum and colon) of MC-fed calves (n=17) at 7, 28, 49, 63 days of age. The results of first study revealed that archaeal, bacterial and fungal communities co-occur in the rumen since early calf development but are impacted differently by pre-weaning diet and age. The inclusion of starter concentrate in the calf diet significantly affected rumen bacterial community by promoting increases of genera, direct and indirectly, related to degradation of readily fermentable carbohydrates (i.e. Megasphaera, Sharpea and Succinivribrio) and depressing those reliant on milk nutrients like lactose (i.e. Lactobacillus, Bacteroides and Parabacteroides). These bacterial changes resulted in apparent diet-driven archaeal differences due to altered fermentation patterns and availability of hydrogen in the rumen that favoured the colonization of members from genus Methanosphaera instead of Methanobrevibacter. No such differences were found for fungi community represented by members from genus Caecomyces and family Neocallimastigaceae, likely due to high inter-animal variation and low fibre content of concentrate used our study. Altogether, this study showed that manipulation of the microbiota in the developing rumen is possible through dietary intervention. Our results may be useful in designing strategies to promote colonization of target communities (i.e. butyrate- producers and lactate-utilizing) linked to functional development of the calf. In regards to second study, bacterial communities in the calf GIT differ qualitatively and quantitatively among compartments and respond differently to age advance that encompass the GIT development (i.e. rumen) and progressive replacement of milk- based to grain-diet (i.e. increase of starter concentrate intake). In the rumen, bacterial community was composed majority by members from genera Prevotella, Butyrivibrio and Ruminococcus whose abundance increased proportionally with age possibly due greater availability of readily fermentable carbohydrates in the rumen. Members from genus Lactobacillus were overrepresented in the jejunum but their predominance was replaced by members from Clostridiaceae family in older calves. The cecum and colon displayed similar abundance at taxa level and the abundance of genera Blautia, Paraprevotella, Prevotella, Phascolarctobacterium and Succiniclasticum increased significantly with age. In summary, our results showed that although there are bacterial communities “common” to distinct regions, a closer look at their structure, abundance and dynamic reveals marked segregation and ecological succession in the calf GIT. Our study adds new insights into bacterial colonization across GIT of pre-ruminant that may be considered in formulating strategies to promote the colonization of target communities aiming improve health (i.e. bacteria with probiotic capability) and performance of dairy calves in the pre-weaning period.

Thesis (Ph. D.)--University of Missouri-Columbia, 2008.<br>The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Vita. "May 2008" Includes bibliographical references.

Standard practice within the dairy industry is to separate calves from the dam immediately after birth and raise calves in individual pens during the milk-feeding period with little or no contact with conspecifics. I reviewed empirical work (Chapter 2) on the social development of calves, the effects of social isolation and the practices associated with group housing of dairy calves. From this review I identified literature gaps that were explored in the following chapters. In Chapter 3, I explored how pairing age affects performance and feeding behaviour development in dairy calves. Early pairing (3 d of age) increased solid feed intake and weight gains in comparison to late-pairing (42 d of age) and individual housing. In Chapter 4, I investigated how individual housing of calves affects food neophobia. The results suggested that calves raised in a complex social environment are less reluctant to ingest new feed types. Chapter 5 investigated whether being grouped with experienced dairy cows would affect the development of grazing behaviours in pregnant dairy heifers first introduced to pasture. The results indicated that grouping heifers with pasture-experienced cows improves grazing behaviour in the first hours following introduction to pasture. Chapter 6 assessed whether weaned calves would sort a total mixed ration (TMR) and if sorting was affected by the availability of a separate grain source. I found that calves can sort a total mixed ration and that the provision of a separate source of concentrate reduces sorting. I conclude that calves raised in more complex social environments early in life experience benefits related to feeding behaviour development, performance, ability to cope with novelty, and that experienced companions can be used to mitigate stress associated with novelty.<br>Land and Food Systems, Faculty of<br>Graduate

The studies reported in this thesis investigated the effects of colostrum management and passive transfer on immunocompetence development in dairy calves. Study 1 involved a survey of 21 commercial dairy farms across Northern Ireland (Nl). Fifty-six percent of the colostrum produced on these farms was satisfactory in terms of colostral IgG concentration. Factors associated with colostral IgG concentration during multivariate analysis were parity and hours from calving to colostrum collection. A range of physical and environmental factors were associated with the nutritional composition of colostrum. Study 2 investigated the effects of maternal nutrition and colostrum feeding volume on calf health, immunity and performance. Concentrate supplementation during the dry period had no effect (P < 0.05) on colostral IgG or calf sera IgG concentration, however did cause an increase in colostrum yield. Calves that received 10% (BW) in colostrum had a greater IgG concentration in their blood for the first 3 d post birth compared to calves receiving 5%BW. In study 3, two laboratory techniques used to directly assess the concentration of IgG in colostrum and calf sera were compared. It was established that both test kits provided a good level of reliability and both kits showed strong correlation with each other. However, the absolute values produced from both kits were dissimilar. Study 4 demonstrated how maternal antibodies were transferred from dam to calf via colostrum intake. Colostrum treatment group had no effect on the level of antibodies produced by the calves when vaccinated at 3 wk of age against BRSV, and again at 49 d when they were given a booster vaccine. No immune response was apparent after the primary BRSV vaccination, however an increase in antibody titre post booster was observed. Passive immune status had no effect (P > 0.05) on the blood metabolites measured to indicate distress at time of weaning (d 56). Study 5 focused on the changes in the dairy calf’s whole blood transcriptome pre and post colostrum feeding during the first week of life. The three main over-represented pathways at both time periods were cytokine-cytokine receptor interaction, complement and coagulation cascades, and intestinal immune network for immunoglobulin A (IgA) production. Immunoglobulin G concentrations were greatest in the calves sera at 48 h post birth (15.2 ± 5.01 mg/mL), compared to concentrations at 0 h (0.64 ± 0.23 mg/mL), 72 h (13.5 ± 3.68 mg/mL), and 168 h (9.01 ± 3.08 mg/mL).

Poor health and growth of young dairy calves can have lasting effects on development and future production. This study aimed to benchmark calf-rearing outcomes in a cohort of Canadian dairy farms, report these findings back to producers alongside their veterinarians, and document the results. A total of 18 Holstein dairy farms, located in the Fraser Valley region of British Columbia, were recruited and surveyed on current colostrum and feed management practices of pre-weaned calves. Blood samples were collected from 1 to 7 day old calves to estimate serum total protein levels by digital refractometry. Failure of passive transfer (FPT) was determined using a total protein threshold of 5.2 g/dL. Average daily gains (ADG) were estimated from 1 to 70 day old pre-weaned heifers using heart-girth tape measurements with early (≤ 35 days) and late (> 35 days) period growth also analysed separately. At first assessment, the average farm FPT rate was 16%. Overall ADG was 0.68 kg/day, with early and late period growth rates of 0.50 and 0.86 kg/day, respectively. Following delivery of benchmark reports, all participants volunteered to undergo a second assessment. The majority (83%) of participants elected to make at least one colostrum or feed protocol change between data collection periods, including increased colostrum at first feeding, increased initial and maximum daily milk, and reduced time to first colostrum. Farms that made such changes experienced improved outcomes; average FPT rates were reduced by 9% and ADG was increased by 0.06 kg/day for all calves, and by 0.16 kg/day for calves less than 36 days old. These results indicate that benchmarking FPT and ADG can motivate producer engagement on calf care, leading to improved production and welfare outcomes for calves on farms that apply relevant management changes.<br>Land and Food Systems, Faculty of<br>Graduate

This study investigated the microbial colonization and maternal influences on the neonatal calf gut microbiome. Microbiome samples were collected from dams (n = 6) and calves (n = 6) using sterile flocked swabs. The vaginal, oral, and fecal bacterial communities were examined from the dam and the fecal community of calves was examined from birth to 60 d of age. Microbial communities varied by anatomical location and age of the calf. Metagenomic analysis 16s ribosomal DNA revealed ten phyla associated with microbiomes of the dam and the same ten phyla associated with calf feces at various time points: Bacteroidetes, Firmicutes, Proteobacteria, Actinobacteria, Cyanobacteria, Verrucomicrobia, Spirochaetes, Tenericutes, Fibrobacteres, and Lentisphaerae. Overall, the calf meconium and fecal microbiome is influenced by a combination of the maternal vagina, oral, and fecal microbiomes. Further studies will be needed to identify the transference mechanisms of maternal microbes to offspring and the associated host-microbial interactions.<br>Master of Science in Life Sciences<br>This study investigated the microbial colonization and maternal influences on the neonatal calf gut microbiome. Microbiome samples were collected from dams (n = 6) and calves (n = 6) using sterile flocked swabs. The vaginal, oral, and fecal bacterial communities were examined from the dam and the fecal community of calves was examined from birth to 60 d of age. Microbial communities varied by anatomical location and age of the calf. Metagenomic analysis 16s ribosomal DNA revealed ten phyla associated with microbiomes of the dam and the same ten phyla associated with calf feces at various time points: Bacteroidetes, Firmicutes, Proteobacteria, Actinobacteria, Cyanobacteria, Verrucomicrobia, Spirochaetes, Tenericutes, Fibrobacteres, and Lentisphaerae. Overall, the calf meconium and fecal microbiome is influenced by a combination of the maternal vagina, oral, and fecal microbiomes. Further studies will be needed to identify the transference mechanisms of maternal microbes to offspring and the associated host-microbial interactions.

There has been little research conducted on the physiological response of calves to temperatures outside thermal neutrality and its effects on intake and weight gain. The effects of ambient temperature on Holstein dairy calves intakes and weight gain were evaluated over a 12-month period. Ambient temperature was monitored using a weather station located 1.3 kilometers from the Utah State University Caine Dairy. Calf health was monitored daily using the University of Wisconsin-Madison School of Veterinary Medicine scoring criteria. Calves were fed whole milk and free choice calf starter. Weight gain, hip height, starter intake, and weather data (temperature, wind speed, relative humidity, precipitation, and barometric pressure) were averaged for 7-day intervals beginning at birth through 13 weeks of age. A regression model was developed including starter intake, milk intake, hip and wither height, calf heath scores, and weather data with weight gain as the dependent variable for each of the 4 seasons of the year. The fall season (September, October, and November) had a negative impact on calf intake and weight gain (averaging 20 pounds (9.1 kilograms) less at 2 months) than other seasons. Calves raised in the winter months also ate significantly more starter, but had the same weight gain as other seasons. Environmental stress factors impact animal welfare and animal productivity, which in turn impacts the economics of the dairy operation and should also be used in determining husbandry practices.

The dairy industry today is beginning to dedicate more focus on the growth of the calf from birth to first breeding to better improve the milk production as well as the overall performance of the individual cows. While the development of the rumen is one of the most vital contributors to the performance of the calf, it remains unknown what molecular mechanisms are responsible for the development of the rumen, and more specifically the proliferation of rumen epithelial cells. The objectives of this study were to investigate the existing data on rumen development through meta-analysis and to explore the effects of sodium butyrate and lipopolysaccharide (LPS) on rumen development in calves through experiment. In the first study a meta-analysis was performed to summarize the literature on calf performance and derive equations that relate rumen (e.g., rumen pH, reticulorumen weight, papillae area) and non-rumen factors (e.g., feed composition, form of feed, housing) to animal performance (e.g., intake of milk replacer (MR), starter, and forage; average daily gain (ADG); and feed efficiency). We looked at four different relationships to further investigate the connections between rumen, non-rumen, and performance factors. In the first and second relationships of interest, the effect of dietary and environmental variables on rumen variables and performance variables were examined, respectively. The third relationship of interest was how rumen variables influenced performance variables. The final relationship of interest was investigating the additive effects of the rumen, dietary, and environmental variables on the performance variables. Forward selection, multiple regression was used to derive equations to select variables that explained variation in the response variable in each model. Results showed that the variation in calf ADG was explained by daily forage intake, calves that were weaned, total starter intake, and total MR intake (concordance correlation coefficient (CCC) = 0.976). The variation in feed to gain ratio was explained by the weight of the ruminal contents, daily forage, MR, and starter intakes, percent of starter in the diet, and total starter intake (CCC = 0.992). The variation in daily forage intake was explained by the percent of the diet that was starter or MR (CCC = 0.998). The variation in daily starter intake was explained by the percent of acid detergent fiber in the starter, a pelleted starter (versus a texturized), diets including starter and forage (versus a milk replacer only diet), and the percent of the diet that was MR (CCC = 0.998). The variation in daily MR intake was explained by the percent of the diet that was starter, final body weight, ruminal propionate concentration, and daily starter intake (CCC = 0.918). Based on these analyses, although dietary and environmental factors are closely associated with calf performance, ruminal factors such as volatile fatty acid (VFA) concentration and ruminal contents appear to have additional, additive influences on calf performance. In the second study, 24 Holstein bull calves were challenged with oral doses of LPS and sodium butyrate. The hypothesis here was that LPS and sodium butyrate would instigate rumen cell proliferation independently and additively. Calves were assigned to one of four treatments: control (CON; n=5), butyrate (BUTY; n=5), LPS only (LPS-O) (n=6), or LPS plus butyrate (LPSB; n=6). All treatments were administered orally twice daily consisting of either: 0.9% saline (CON); 11 mM sodium butyrate (BUTY); LPS ranging from 2.5 to 40 µg/kg metabolic body weight (BW0.75, LPS), or both butyrate and LPS (LPSB). Calves were fed milk replacer (22% CP, 20% fat, as-fed) and starter (20% CP, 3% fat, as-fed) based on metabolic BW, or about 12% BW of MR and 3% BW of starter. Feed intake, fecal and respiratory scores, and rectal temperature were recorded daily. Calf BW, hip height, jugular blood samples, and rumen content samples (via oroesophageal tube) were collected weekly. Calves were weaned at 6 wk of age and euthanized at 8 wk of age, whereupon ruminal weights and ruminal samples for papillae area and epithelial thickness were collected. Blood and rumen samples were analyzed for concentrations of beta-hydroxybutyrate, glucose, LPS-binding protein, and VFA. Data were analyzed as a 2x2 factorial with the repeated effect of week. Three non-orthogonal contrasts (CON versus the average of all other treatments; LPS-O versus LPSB, and LPSB versus BUTY) were investigated. Feed intake, health measures, and blood metabolites did not differ by treatment. Calf BW increased by week (P < 0.0001). Irrespective of week, LPS calves weighed more and had higher ADG than BUTY calves (P = 0.020). Irrespective of week, withers height was greater in LPS compared to CON (P = 0.006). Rumen pH and rumen VFA concentrations did not differ by treatment but did decrease and increase, respectively, with week in conjunction with increased starter intake. Total empty forestomach (P = 0.014) and reticulorumen weights (P = 0.012) were greater in LPSB compared to BUTY. Overall, LPS and sodium butyrate appeared to have synergistically affected some, but not all rumen measurements without affecting calf growth, intake, or health. Results from the meta-analysis emphasize the importance of continuing to focus on the solid feed intake of the calf from birth through weaning. Implications from the LPS study are imperative to other dairy scientists who will attempt to further study the effects of LPS on the rumen.<br>Master of Science in Life Sciences<br>Dairy calves are born with an under-developed stomach. The stomach has four compartments: the rumen, reticulum, omasum, and abomasum. The rumen is the largest component where finger-like projections called papillae grow to absorb nutrients for the calf. It is vital to the calf that the rumen develops not only the papillae to absorb nutrients but also to foster a microbe-rich environment so the microbes can act as a defense mechanism for the calf to aid in fighting disease. While it is known that things like solid feed support the development of the rumen, the mechanism behind how that is happening still remains unclear in the literature. The objective of this study was first to better understand the relationships that exist in the literature between dietary, environmental, and ruminal factors, and second to investigate the claim that certain components of the bacteria in the rumen are stimulating rumen development independently and additively with sodium butyrate. In order to investigate the relationships amongst the dietary, environmental, and ruminal parameters, a computer program called R Studio was used to analyze over 30 different models that extracted data from a database that included a collection of 36 studies from the literature. This is also known as a meta-analysis. The associations of interest that we found were: average daily gain (ADG) of the calf was associated with daily forage intake, calves that were weaned, total starter intake, and total MR intake. Feed efficiency of the calf was associated with the weight of the ruminal contents, daily forage, milk replacer (MR), and starter intakes, percent of the diet composed of starter, and total starter intake. Daily forage intake was associated with the percent of the diet that was starter or MR. Daily starter intake was associated with acid detergent fiber in the starter, a pelleted starter (versus a texturized starter), diets including starter and forage (versus a MR only diet), and the percent of the diet that was MR. Daily MR intake was associated with the percentage of the diet that was starter, final body weight (BW), ruminal propionate concentration, and daily starter intake. These relationships emphasized that although dietary and environmental factors are more closely associated with calf performance, ruminal factors such as rumen contents and volatile fatty acid concentrations appear to have additional, additive influences on calf performance. The second part of the study objective was to explore an idea that, to our knowledge, has not been published in the literature. In the second study, 24 dairy calves were challenged with oral doses of a gram-negative bacteria lipopolysaccharide (LPS), and a short-chain fatty acid sodium butyrate. The hypothesis in this study was that the LPS and sodium butyrate would trigger metabolic pathways on the rumen cell membranes to a greater extent together, versus independently, to increase the amount of cells growing. Calves were assigned to one of four treatments: control (CON), butyrate (BUTY), LPS only (LPS-O), or LPS plus butyrate (LPSB). To study this effect, each treatment group was administered their respective treatment orally as a liquid twice daily. To measure the results, the following data was collected: feed intake, fecal and respiratory scores, rectal temperature BW, hip and withers height, blood samples, rumen content and pH samples, papillae area, epithelial thickness, and organ weights. Blood and rumen samples were analyzed for blood metabolites and volatile fatty acids concentrations respectively. Data were analyzed and results showed no difference amongst feed intake, health measures, rumen pH, rumen VFA concentration, and blood metabolites by treatment. Calves on the LPS treatment weighed more and had higher ADG than BUTY treatment calves. Withers height was higher in the LPS group when compared to CON. Stomach weights were higher in the LPSB group when compared to the BUTY group.

The objective was to summarize management practices, identify factors associated with bacterial counts, and describe the variation in total solids concentrations of milk or milk replacer in automated feeders. Six dairy calf operations in Virginia and 4 in Minnesota employing 1 to 2 sophisticated automated calf feeders were visited biweekly for 26 to 28 wk. An initial management survey was conducted for each farm. Observations on facilities, calf weights and heights, blood samples to estimate serum total proteins, treatment records, digital feeding behavior records, and milk or milk replacer (MMR) samples were collected at each visit. Additional milk replacer (MR) samples were collected for 4 wk pre- and post-circuit cleaning. Samples of MMR were plated on Aerobic Plate Count (APC) and Coliform Count (CCP) Petrifilms. Total solids concentration was estimated for MR samples by refractometry. Feeding plans varied widely between farms. Estimates of calf growth were near industry standards, but the proportion of calves receiving treatment was elevated. Least squares mean APC and CCP were 5.26 and 3.01 log10 cfu/ml for Virginia and 3.80 and 0.61 log10 cfu/ml for Minnesota. Circuit cleaning (CC) caused 13 and 16% log reduction in APC and CCP. However, more frequent CC/wk increased bacteria. Mixer/heat exchanger cleanings decreased bacteria during biweekly farm visits. Chlorine bleach reduced bacteria. Use of silicone feeder hoses increased bacteria. A quadratic effect of MMR liters delivered/d was observed; liters delivered > 147 L decreased APC. Automated feeders delivered 12.26% of MR samples > 2% over and 25.71% > 2% under target solids concentration.<br>Master of Science

Master of Science<br>Animal Sciences and Industry<br>Lindsey E. Hulbert<br>Rapid responses in milk production to changes in dairy cow management, nutrition, and health give producers feedback to help optimize the production and health of dairy cattle. On the contrary, a producer waits up to two years before the investments in calf growth and health are observed thru lactation. Even so, performance, health, and immune status during this time play a large role in subsequent cow production and performance. A recent report from the USDA’s National Animal Health Monitoring System estimated that 7.6 to 8.0% of dairy heifers die prior to weaning and 1.7 to 1.9% die post-weaning (2010). The cost of feed, housing, and management with no return in milk production make for substantial replacement-heifer cost. Therefore, management strategies to improve calf health, performance, and immune function are needed. Prebiotic supplementation has gained interest in recent years as a method to improve gastrointestinal health and immune function in livestock. It has been provided that prebiotic supplementation may be most effective in times of stress or increased pathogen exposure throughout the calf’s lifetime (McGuirk, 2010; Heinrichs et al., 2009; Morrison et al., 2010). Multiple studies have researched the effect of prebiotics around the time of weaning, but to the author’s knowledge, none have focused on prebiotic’s effects during the transition from individual housing prior to weaning to commingled housing post-weaning which may also be a time of stress or increased pathogen exposure. Therefore, a study was conducted to determine the effects of prebiotic supplementation of mannan-oligosaccharide and beta-glucan during this commingling phase. The results indicate that prebiotic supplementation alters feeding behavior, modulates neutrophil function, and increases antibody response during this time. The purpose of industry-based research, such as studies on prebiotics and other methods to improve calf health and performance, is to provide producers with tools to advance and improve their operations. In this respect, it is beneficial to learn what producers’ needs are and what they are interested in improving. An extension survey was conducted to establish priorities, need, and management practices of Kansas dairy producers. The results of the survey indicate that nearly half of the producers (49.3%) are interested in extension programs focused on calf/heifer management. Similarly, over half (54.8%) of the producers responded that they are interested in improving calf/heifer management in the next 5 years. The death loss observed as well as the results of the survey display a need and a producer desire to improve calf management, warranting research on prebiotics and further methods to continue to improve calf health and performance

Es varen realitzar quatre estudis per avaluar l'efecte de donar molta llet a les vedelles lactants durant la fase de lactància, per tal de millorar el creixement de les vedelles de reposició durant aquest període. Els vedells que varen rebre una alimentació mÎs rica en llet durant la lactància van créixer més, però van menjar menys pinso que els vedells que seguien una alimentació convencional. Tot i així, després del deslletament ambdos nivells d'alimentació van presentar el mateix ritme de creixement i consum de pinso. Per altra banda, el fet de criar vedells en grup i amb un nivell elevat de llet durant la lactància, no va estimular el consum de pinso en comparació als vedells criats individualment i alimentats amb un alt nivell de llet. A més a més, els index productius de creixement i l'aparició de problemes de salut van ser similar en vedells criats en grup o individualment. En general, els vedells criats en grups varen augmentar els comportaments orals amb finalitat no nutritiva, i disminuir els comportaments de succions creuades i succions dirigides a la zona pèlvica al llarg de l'estudi. Tant els vedells criats en grups com individualment van presentar un lleuger augment de la conducta de "selfgrooming" al llarg de l'estudi. La concentració plasmàtica d'amino àcids va indicar que cap amino àcid limitava el creixement durant la fase de lactància quan les vedelles es varen criar seguint una alimentació amb un alt nivell de llet. No obstant, en els vedells que es van criar convencionalment, les concentracions plasmàtiques de fenilalanina i triptòfan una hora després de menjar estaven positivament correlacionades amb el guany mig diari, i negativament correlacionades amb la concentració plasmàtica d'urea, suggerint que els creixements dels vedells criats convencionalment podria estar limitat per l'aportació d'aquests dos amino àcids quan s'utilitza una llet maternitzada i un pinso similar al d'aquest estudi. Per altra banda, la menor excreció urinària de derivats púrics observada en vedelles alimentades amb un alt nivell de llet en comparació a les vedelles criades convencionalment, va indicar un menor fluxe microbià a nivell duodenal que podria estar relacionat amb la menor ingestió de pinso en les vedelles alimentades amb un nivell elevat de llet durant el periode de lactància. A més a més, els vedells alimentats amb un nivell alt de llet durant la fase de lactància van tenir una menor digestibilitat aparent dels nutrients del pinso la setmana després del deslletament en comparació als vedells alimentats convencionalment. Les concentracions sèriques de glucosa i insulina varen ser majors en vedells alimentats amb un alt nivell de llet que en vedells alimentats convencionalment. Però, les concentracions sèriques d'urea no varen seguir un mateix patró en els diferents estudis. En dos dels tres estudis, les concentracions sèriques d'urea van ser superiors en vedells criats convencionalment que en aquells alimentats amb un alt nivell de llet, però en l'altre estudi les concentracions sèriques d'urea varen ser similars en ambdos nivells d'alimentació. Finalment, l'avantatge de pes viu aconseguit durant la fase de lactància en vedelles seguint una alimentació amb un alt nivell de llet es manté numèricament superior fins els 385 d d'estudi, però aquest avantatge no redueix l'edat a la primera cubrició, i ni millora la fertilitat a la primera cubrició en vedelles criades amb un alt nivell de llet en comparació amb vedelles criades convencionalment<br>Four studies were conducted to evaluate the effects of feeding dairy calves on an enhanced-growth feeding program. Enhanced-fed calves showed greater average daily gain, but lower starter dry matter intake than calves fed conventionally during the preweaning period. However, after weaning both feeding programs resulted in similar rates of growth and starter consumption. On the other hand, rearing enhanced-fed calves in groups did not stimulate starter intake. Also, performance was not decreased nor the occurrence of health problems increased when calves were reared in groups. In general, calves raised in groups increased non-nutritive oral behavior, and decreased cross-sucking and inter-sucking behaviors throughout the study, and both individually-and groupedreared calves slightly increased self-grooming behavior throughout the study. Plasma amino acid concentrations indicated that none amino acid was limiting growth during the preweaning period when calves were raised following an enhanced-growth feeding program. Nevertheless, with calves conventionally-fed, plasma phenylalanine and tryptophane concentrations one hour after feeding were positively correlated with average daily gain and negatively correlated with plasma urea concentrations, suggesting that growth of calves following conventional feeding programs could be limited by the supply of these two amino acids when using milk replacers and starters similar to those used in the present study. On the other hand, lower total purine derivatives urine excretions were observed in enhanced-compared with conventionally-fed calves, suggesting a lower microbial duodenal flow that was probably related to the low starter intake during the preweaning period of enhanced-fed calves. Furthermore, apparent nutrient starter digestibility was lower in enhanced-compared with conventionally-fed calves the week after weaning. Serum glucose and insulin concentrations were greater in enhanced-than in conventionally-fed calves, but serum urea concentrations did not follow a common pattern among studies. In two out of the three studies, serum urea concentrations were greater in conventionally-than in enhanced-fed calves, but in the other studies there were no differences between treatments. Body weight advantage obtained with enhancedgrowth feeding program was numerically maintained later in life, but this advantage did neither reduce the age at breeding, and nor improve fertility at first breeding of enhancedfed calves.

Animal behavior can be used to detect disease and well-being in dairy cattle. In this dissertation, we evaluated the accuracy of an accelerometer to measure step activity, lying time, and lying bouts in pre-weaned dairy calves. The output from the accelerometer was correlated with behavioral measurements taken from video footage. The accelerometer proved to be accurate in identifying step activity (r = 0.99), lying time (r = 0.99), and lying bouts (r = 0.99). The accelerometer was then used to detect behavioral changes occurring around respiratory disease events in pre-weaned calves. Activity declined 1 d prior to clinical disease onset, and this decline persisted for 3 d post-diagnosis. Furthermore, lying bouts declined beginning 2 d prior to diagnosis, and this effect persisted after diagnosis as well. However, aside from a slight reduction in milk intake, feeding behavior was not different between diseased and healthy calves. These data suggest that activity and lying behaviors may be a better measure than feeding behaviors for detection of respiratory disease in pre-weaned dairy calves. Dystocia has detrimental effects on both periparturient dairy cows and newborn calves. We administered a non-steroidal anti-inflammatory drug, meloxicam to periparturient dairy cattle. Treatments included administration prior to calving (MEL-PRE, n = 60), post-calving (MEL-POST, n = 69), or a negative control (CTL, n = 65). We measured the length of labor to determine which cows had easy or difficult calvings. Eutocic MEL-PRE animals produced 6.8 kg/d more milk than eutocic CTL. Regardless of calving difficulty, MEL-PRE animals produced more milk fat, protein, and lactose (kg/d) than the CTL. Additional research is needed to determine appropriate treatments for dystocic calvings. Calves born during the above trial were monitored to determine if meloxicam administration prior to calving impacted newborn calf health and behavior. Calves born difficultly displayed fewer lying bouts for the first few days after birth when compared to calves born easily. No effect of treatment or calving difficulty was noted on calf health. Additional research examining intervention strategies aimed at improving well-being of calves born difficultly is needed.<br>Ph. D.

Mortality and decreased weight gain resulting from infection and disease in dairy calves is a problem within the dairy industry. Colostrum is the sole source of maternal immunity for the calf, having a substantial impact on health and survival. To date, colostrum quality is determined by concentration of antibodies. Colostrum also contains proteins and cells, which may enhance immune development in the neonate. Our goals were to determine the impact of colostral immune cells on (1) immune status during the first month of life and (2) immune development over time. To determine the impact of adoptively transferred colostral immune cells, calves were fed either whole colostrum (WC) or cell-free colostrum (CFC) at birth. During the first month of life, calves fed CFC had decreased numbers of CD4+ T cells when compared to WC-fed calves. However, CFC-fed calves had a greater percentage of monocytes during the first month of life. To determine the influence of colostral immune cells on immune development, cellular blood parameters were measured in response to two series of vaccinations (A and B). After vaccination series A, CFC-fed calves had decreased numbers of B cells when compared to WC-fed calves. After vaccination series B, CFC-fed calves had decreased levels of interleukin-2 gene expression and numbers of CD4+ and gamma delta T cells when compared to WC-fed calves. This study demonstrates that colostral immune cells impact immune status and development in dairy calves.<br>Master of Science

Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-10-25T12:49:30Z No. of bitstreams: 1 texto completo.pdf: 607849 bytes, checksum: 8fcbae0fc9246bf1307217869595d65f (MD5)<br>Made available in DSpace on 2017-10-25T12:49:30Z (GMT). No. of bitstreams: 1 texto completo.pdf: 607849 bytes, checksum: 8fcbae0fc9246bf1307217869595d65f (MD5) Previous issue date: 2017-07-21<br>Objetivou-se avaliar o efeito da suplementação de monensina (MON), probióticos ou óleos essenciais sobre o desempenho e índice de escore fecal (IEF) dos bezerros leiteiros de 6-60 d de idade e seu efeito residual 15 dias após o desmame. Cinqüenta bezerros da raça Holandesa foram alimentados com 5 L de leite cru por dia mais concentrado inicial até o desmame. Os tratamentos foram: Controle (CON), adição de MON (30 mg / kg de concentrado), probiótico E. faecium (PROB, 70 mg / kg de concentrado, CFU / kg 7,0E + 09, Cylactin®), óleos essenciais (OE, 300 mg / kg de concentrado, CRINA® Ruminants), ou adição de PROB + OE (EOPROB). O consumo do alimento e o escore fecal (pontuado de 1 a 4) foram medidos diariamente e os animais foram pesados a cada 15 dias. Foi realizada a extração de DNA das fezes, para identificar por meio da PCR a presença ou ausência de microorganismos (E. coli, Hafnia, Shiguella, Lactobacillus spp, Enterococcus spp e Enterococcus faecium NCIMB 10415). Dois ensaios de digestibilidade de 72 h foram realizados nos dias 20-28 (período 1) e 50-56 (período 2), por coleta fecal total. O experimento foi definido em blocos inteiramente casualizados com dez repetições por tratamento e data de entrada usada como bloco. A ANOVA foi realizada para testar os efeitos do tratamento em P < 0,10, as medias foram comparadas pelo teste t de Student e os resultados da PCR foram analisados pelo teste de Wald. O consumo de matéria seca (CMS) antes do desmame foi maior (P < 0,05) para OE (903,03 g / d) em comparação com MON (794,34 g / d) e EOPROB (783,12 g / d). Animais OE e MON diminuíram (P < 0,012) o IEF durante o aleitamento. O ganho médio diário (GMD) e a eficiência alimentar (EA) não diferiu (P > 0,10) entre os tratamentos antes do desmame. A altura à cernelha (AC) e altura à garupa (AG) não foi diferente entre os tratamentos (P > 0,10) antes nem depois do desaleitamento. Após o desmame, o CMS e IEF não diferiu entre os tratamentos (P > 0,10). OE apresentou maior GMD (917,50 g / d) (P < 0,05) em comparação com CON (615,80 g / d) e PROB (592,60 g / d). A EA melhorou (P < 0,05) com OE (0,72 g / g) sobre o CON (0,36 g / g), MON (0,49 g / g) e PROB (0,36 g / g). Os resultados de PCR mostraram ausência do E. faecium NCIMB 10415 em animais PROB e COM. Durante os ensaios de digestibilidade, houve maior consumo (P < 0,001) de nutrientes nos dias 50-56 em comparação com os dias 20-28. Animais PROB apresentaram maiores (P < 0,05) consumo de MS (1184,56 g / d), proteína bruta (PC) (254,63 g / d) e fibra detergente neutra (FDN) (320,36 g / d) comparado com EOPROB. A ingestão de carboidratos no fibrosos (CNF) foi maior (P < 0,05) no tratamento OE (384,31 g / d) comparado com CON (323,63 g / d), MON (323,84 g / d) e EOPROB (301,30 g / d). A ingestão de extrato etéreo (EE) e matéria orgânica (MO) não foi afetada (P > 0,10) pelos tratamentos. A digestibilidade da FDN foi maior (P < 0,012) em animais alimentados com MON (924 g / d). Em conclusão, OE pode ser adicionado à ração de bezerros leiteiros para melhorar o escore fecal, aumenta o CMS e melhora a digestibilidade dos nutrientes. O IEF no pré-desmame diminuiu com MON e aumentou com PROB<br>We aimed to evaluate the effect of supplementation with monensin (MON), probiotics or essential oils on performance and fecal consistency index (FCI) of suckling dairy calves from 6-60 d of age, and its residual effect 15 d after weaning. Fifty Holstein calves were fed 5 L of raw milk per day plus starter concentrate until weaning. The treatments were: Control (CON), adition of MON (30 mg/kg of starter), probiotic E. faecium (PROB, 70 mg/kg of starter, CFU/kg 7,0E+09, Cylactin ® ), essential oils (EO, 300 mg/kg of starter, CRINA ® Ruminants), or addition of PROB +EO (EOPROB). DMI and fecal score (scored from 1 to 4) were daily measured, and animals were weighed every 15 d. DNA extraction from feces was performed, to identifying by PCR the presence or absence of microorganisms ( E. coli, Hafnia, Shiguella, Lactobacillus spp, Enterococcus spp, and Enterococcus faecium NCIMB 10415) in the feces. Two 72 h digestibility trials were performed at days 20-28 (period 1) and 50-56 (period 2), by total fecal collection. The experiment was designed in completely randomized block with ten replications per treatment, and date of entrance used as block. ANOVA was performed to test treatment effects at P < 0.10, means were compared by Student's t-test, and PCR results were analyzed by Wald test. The dry matter intake (DMI) before weaning was greater (P < 0.05) for EO (903.03 g / d) compared to MON (794.34 g / d) and EOPROB (783.12 g / d). EO and MON decreased (P < 0.012) FCI during pré-weaning. Average daily gain (ADG) and feed efficiency (FE) did not differ among treatments (P > 0.10) before weaning. The withers height (WH) and croup height (CH) was no different among treatments after or before weaning. After weaning the DMI and FCI did not differ among treatments (P > 0.10). EO had greater (P < 0.05) ADG (917.50 g / d) compared to CON (615.80 g/d) and PROB (592.60 g / d). The FE improved (P < 0.05) with EO (0.72 g / g) over CON (0.36 g / g), MON (0.49 g / g) and PROB (0.36 g / g). The PCR results showed absence of E. faecium NCIMB 10415 in animals fed PROB and CON. During the digestibility trials, greater intakes (P < 0.001) of nutrients were observed at days 50-56 compared to 20-28 days. Animals fed PROB had greater (P < 0.05) intakes of DM (1184.56 g / d), crude protein (CP) (254.63 g /d) and neutral detergent fiber (NDF) (320.36 g / d) than animals fed EOPROB . Intake of Non-fibrous carbohydrates (NFC) were greater (P < 0.05) in EO (384.31 g / d) compared to CON (323.63 g / d), MON (323.84 g / d) and EOPROB (301.30 g / d). The ether extract (EE) and organic matter (OM) intake was not affected (P > 0.10) by treatments. NDF digestibility was greater (P < 0.012) in animals fed MON (924 g / d). In conclusion, EO can be added to the dairy calf ration to improve fecal score, increases DMI and improves nutrient digestibility. The pre-weaning FCI decreased with MON and increased with PROB

Exposure to antibiotics has the potential to increase the incidence and proliferation of antibiotic resistance genes (ARG) in the gut and fecal microbiome. Non-saleable, antibiotic-containing milk from cows treated with antibiotics (waste milk) is commonly fed to dairy calves but the effects of ingestion of antibiotics at an early age on the gut microbiome and the development of ARG in the naive gut are not well understood. Pirlimycin, a lincosamide antibiotic acting against Gram positive bacteria through inhibiting protein synthesis by binding to the 50S ribosome, is commonly used as mastitis therapy. Lincosamides are also considered highly important in human medicine, often used against Staphylococcus aureus and Clostridium difficile infections. Emerging microbial resistance to pirlimycin is of concern for both animal and human health. The objective of this study was to determine the effect of early lincosamide antibiotic exposure on the abundance of ARG in feces of milk-fed calves. Eight female Holstein calves were blocked by age, paired by block, and randomly assigned to pasteurized whole milk (control; n = 4) or milk containing 0.2 mg/L of pirlimycin (treatment; n = 4). Calves were enrolled after receiving two colostrum feedings and were fed 5.68 L of pasteurized whole milk, treatment, or control, divided into two daily feedings, from d 1 to d 50 of age. After weaning calves were fed non-medicated starter grain ad libitum. Fecal samples were collected weekly until 85 d of age and freeze-dried. DNA was extracted using QiaAmp® Fast DNA Stool Mini Kit and qPCR was used to quantify the absolute abundance (gene copies/g of wet feces) and relative abundance (gene copies/copies of 16S rRNA genes) of erm(B), tet(O), tet(W) and 16S rRNA genes. Data was analyzed using PROC GLIMMIX in SAS. Abundance of 16S rRNA genes, tet(O) and tet(W) were not different between control and pirlimycin-fed calves nor were the relative abundance of tet(O) (mean = 0.050 tet(O) copies/16S rRNA genes) or tet(W) (0.561 tet(W) copies/16S rRNA genes). While abundance of erm(B) was higher in pirlimycin-fed calves compared to control calves (6.46 and 6.04 log gene copies/g wet feces; P = 0.04) the relative abundance of erm(B) (0.273 gene copies/16S rRNA genes) in feces of calves was not influenced by treatment. There was an effect of day (P < 0.10) for absolute abundance of tet(O), tet(W), and erm(B) indicating that the levels change with time as the fecal microbiome develops. This study suggests that feeding pirlimycin-containing non-saleable milk to growing calves may increase environmental loading of erm(B), which codes for resistance to highly important macrolide and lincosamide antibiotics. Additional research is needed on effects of feeding waste milk to calves on other fecal ARG and on the post-excretion and post-application fate of these genes.<br>Master of Science

The objective of this study was to determine if pair housing using a modified calf hutch on a commercial dairy farm would provide similar benefits to those previously described in research settings. Despite many benefits (e.g. improved weight gain and reduced fearfulness) of housing calves in small groups, individual calf hutches are still common in North America. This study took place on a commercial farm in the lower Fraser Valley region of British Columbia from May to December 2016. A week after birth, calves were randomly assigned to individual (n = 14) or paired (n = 8 pairs) hutches. Our modified pair hutch consisted of 2 individual hutches placed next to each other with both calves having access to both hutches and a common run. Calves were fed milk 2/day (d) using a nipple bottle, 6 Litres (L)/d from d 1 to d 7, 10 L/d from d 8 to d 35, and 6 L/d until d 60 (weaning). Ad libitum access to calf starter (solid food) and water was offered throughout the experiment. Feed intake was measured weekly until calves were 67 ± 5 d old. Body weight (BW) and health measures were recorded weekly until the calves were 88 d old. Calves were exposed to a novel food test at 60 d; the amount of food consumed in 30 minutes, and the latency to approach the novel food was measured. Pair housed calves ate more starter (0.89 (0.72 - 1.08) vs. 0.48 (0.42 - 0.56) kg/d; geometrical mean (confidence interval)) than individually housed calves. Pair housed calves also ate almost 3 times more food during the novel food test (154.13 ± 26.85 vs. 57.84 ± 19.55 g). There was no difference in BW or in the latency to approach the novel food. In conclusion, joining adjacent hutches is an option for pair housing that results in reduced fearfulness and increased solid food intake relative to individual hutches.<br>Land and Food Systems, Faculty of<br>Graduate

Calves infected with Babesia bovis or Babesia bigemina between 3 and 9 months of age can develop immunity without showing overt clinical signs. This transient immunity is not dependent on maternal immunity. After 9 months of age, they are fully susceptible to challenge. Dairy calves between 2 and 3 months of age were vaccinated with B. bigemina and B. bovis live frozen vaccines (Onderstepoort Biological Products®). Two months after vaccination, 90% of calves were serologically positive on IFA test to B. bigemina, and 70% were serologically positive to B. bovis. At this age, only 17% of the control group had seroconverted to B. bigemina and none of the calves had seroconverted to B. bovis. All experimental calves maintained positive serological status to both B. bovis</i. and B. bigemina for at least 5 months after vaccination. It is sound practice to vaccinate dairy calves against babesiosis at 2–3 months of age. Endemic stability is achieved before the period of natural resistance wanes. Copyright<br>Dissertation (MSc)--University of Pretoria, 2011.<br>Veterinary Tropical Diseases<br>unrestricted

The pronounced responses of dairy calves to novel events such as weaning and mixing form an obvious welfare concern and represent an important challenge for the dairy industry. I hypothesized that providing calves a more natural social environment would reduce these responses. This thesis consists of 5 chapters, beginning with a general introduction (Chapter 1) and ending with a general discussion and conclusion (Chapter 5). Chapter 2 compares the effects of individual vs. pair housing on calf responses to weaning from milk as well as on the adjustment to a novel pen and novel social partners at mixing. This chapter shows that being housed with a social companion increases starter intake pre-weaning, has a buffering effect on vocal responses at weaning and improves the performance of calves after mixing when compared to calves housed individually. Chapter 3 describes the effects of housing dairy calves with an older companion on the development of feeding behavior before and after weaning from milk. This chapter shows that a weaned companion is an important social model during weaning, stimulating early intake of hay pre-weaning, starter intake post-weaning and improving growth relative to calves housed in groups of similar age. Chapter 4 describes the effects of the early social environment on the behavioral responses of dairy calves to environmental and social novelty. The results from this chapter show that individually housed calves are more reactive to both environmental and social novelty when compared to pair housed calves. Calves housed with an older companion are also more reactive to separation from group members but less reactive to the presence of an unfamiliar calf when compared to calves housed in groups of similar age. Chapter 5 discusses the results of this thesis and suggests that future research on the development of the affective and cognitive abilities of dairy calves in different social contexts can improve the welfare of commercially reared dairy calves. Providing calves access to conspecifics of similar age or an older companion can minimize calf responses to weaning from milk and reduce responsiveness to environmental and social novelty during mixing.

Pain is one of the most highly studied emotions in animals, and the interaction between pain and cognitive processes is well documented in humans. Recent research has attempted to use changes in cognitive processes as a method of assessing emotions of animals. This approach is based on the influence of mood states on attention to and interpretation of information. Studies with humans have shown that depressed or anxious people interpret ambiguous stimuli more negatively, while people in positive states have more optimistic interpretations. These judgement bias tasks have been applied in different animal species, but none have investigated how pain affects emotional states. Here I present the first report of cognitive bias in cattle and the first evidence of a bias in response to pain in any non-human species. I assessed cognitive bias in dairy calves before and after hot-iron dehorning. Previous work has shown that calves experience pain for at least 24 h after this procedure. Calves (n=17) were trained in a go/no-go task to expect positive (milk reward) or negative (time-out with no opportunity to access milk) outcomes following nose contact with a video screen that was either white or red; calves were alternatively assigned white or red as the positive training stimulus, and the opposite colour as the negative training stimulus. Once calves had learned to discriminate between these two training stimuli, they were tested with unreinforced ambiguous probes (screen colours at 25%, 50%, and 75% red) introduced randomly within training sessions. Probes were presented in sessions 1 d before and 1 d after dehorning. Calves approached the ambiguous probe screens less frequently after dehorning (88±5, 55±5, 11±5 % for the near-positive probe, the halfway probe, and the near-negative probe, respectively) compared to before dehorning (92±5, 68±5, 23±5 %), a difference that was numerically most pronounced for the halfway and near-negative probes. These results indicate that calves experiencing pain during the hours after hot-iron dehorning exhibit a negative "pessimistic" bias and support the use of judgement bias tasks in the assessment of animal emotions.

Dairy calves in the U.K. are currently reared on ‘least cost’ principles, with minimal milk feeding and early weaning to solid foods. This has been described as maintaining the calf in ‘a state of chronic hunger’. As well as repercussions on calf health, growth and welfare, human studies suggest that underfeeding the newborn is a major risk factor for metabolic disease in the adult. The aims of this study were to determine current dairy calf rearing practices across the U.K., to investigate the performance of Holstein heifer calves fed increased milk replacer (MR) compared to restricted volumes, and to determine the impact of this on key performance indicators (KPIs) of these animals as calves and growing heifers. A postal questionnaire was offered to one thousand U.K. dairy farmers to determine current calf rearing practices. The response rate was 72% and revealed that housing and feeding practices were variable between farms. The majority of farmers (93%) fed restricted volumes of milk or milk replacer to their pre-weaned calves. The body weight, withers and loin height, heart and belly girth, crown to rump length, hock-fetlock length and body condition score (BCS) were recorded weekly from birth to 12 weeks and monthly from 12 weeks until conception in two groups of Holstein heifer calves on one commercial dairy farm in the north-west of England, U.K. Calves were assigned to a restricted, Group R (n = 50) or ad libitum, Group A (n = 50) MR feeding strategy from birth until weaning. Growth rates were greater for Group A (0.72kg/day) from birth until 3 weeks than Group R (0.17kg/day). Body condition score increased for Group A during this period (0.1 points) while it decreased for Group R (0.3 points). Thereafter, growth rates were similar between dietary groups although no catch-up growth was observed for Group R animals. Changes in morphometric measures were greater for Group A calves than Group R from birth to 12 weeks. From 12 weeks of age onwards, dietary group differences in morphometric measures disappeared but body weight differences remained until conception. The glucose metabolism and insulin sensitivity of a subset of heifer calves (n = 6 Group A, n = 6 Group R) was investigated at 3, 12 and 39 weeks of age and was shown not to be affected by dietary group. The carcass composition of Holstein bull calves assigned to one of the two dietary groups was assessed. Calves were studied at birth (n = 3), 3 weeks, 9 weeks or 12 weeks (n = 3 per dietary group at each age). Carcass composition was assessed using spiral CT technologies. Group A calves had greater internal adipose deposition at all ages but there was no difference in carcass associated adipose tissue. The age at puberty, first service and conception was between 2 and 3 weeks lower for Group A animals than for Group R. Increased MR feeding of Holstein heifers allows for greater growth rates and earlier entry into the milking herd.

Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-04-03T17:45:15Z No. of bitstreams: 1 texto completo.pdf: 1194926 bytes, checksum: 09f8513613b1934ea53333f3a9b4eb03 (MD5)<br>Made available in DSpace on 2017-04-03T17:45:15Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1194926 bytes, checksum: 09f8513613b1934ea53333f3a9b4eb03 (MD5) Previous issue date: 2017-02-23<br>Conselho Nacional de Desenvolvimento Científico e Tecnológic<br>Este trabalho foi desenvolvido a partir de três estudos. Assim, o objetivo do primeiro estudo foi identificar variáveis que afetam o consumo de concentrado (CC), e desenvolver equações para predizer o CC de bezerros leiteiros até os 64 dias de vida. O banco de dados foi composto pelos dados individuais de 189 bezerros de 8 experimentos, totalizando 6.426 observações diárias de consumo. A informação coletada dos estudos foram: peso corporal ao nascimento (PCi; kg), CC (kg/dia), consumo de leite ou sucedâneo (CL; L/dia), sexo (macho ou fêmea), raça (Holandês ou mestiço Holandês×Gir) e idade (dias). A correlação entre o CC e as variáveis quantitativas CL, PCi, PCi metabólico (PCi0,75) e idade foi estabelecida. Posteriormente, foi realizada uma avaliação gráfica do comportamento padrão dos dados; e um modelo exponencial foi escolhido. Os dados foram avaliados usando a técnica de meta-análise para estimar os efeitos fixos e os efeitos aleatórios associados aos experimentos através de modelos mistos não-lineares. A técnica de validação cruzada foi utilizada para estimar a acurácia e precisão das equações desenvolvidas, com base no quadrado médio do erro de predição (QMEP), coeficiente de correlação de concordância, que foi decomposto em acurácia (Cb) e precisão (ρ). De forma adicional, uma análise tipo “bootstrap” foi utilizada para estimar o viés associado a cada parâmetro das equações desenvolvidas. Uma correlação negativa entre CC e CL foi observada (r= -0,388), no entanto, idade apresentou uma correlação positiva com CC (r= 0.66). Não foi observado efeito do tipo de alimento líquido utilizado (leite ou sucedâneo) no desenvolvimento da equação. No entanto, foram ajustadas 2 equações, significantemente diferente para todos os parâmetros, para predizer o CC para bezerros consumindo menos que 5 (CC<5) ou mais que 5 (CC>5) litros/dia de leite ou sucedâneo: CC<5 = 0,1839±0,0581 × CL × exp((-0,0040±0,0011 × CL + 0,0333 ±0,0021 ) × (I- (6,0332 ±0,3583 × CL + 0,8302± (0,12 × CL); CC>5 = 0,1225±0,0005 × CL × exp((-0,0015±0,0001 × CL + 0,0217±0,0006) ×))) 0,5092 - (I- (1,9508 × CL + 3,5382± )))1,3140 ±0,1710 - (0,12 × CL); onde CC<5 e CC>5 = consumo predito de concentrado para bezerros que consomen menos de 5 ou mais de 5 litros/dia de leite ou sucedâneo, respectivamente (kg/dia); CL = consumo de leite ou sucedâneo (L/dia) e I = idade (dias). Estas equações apresentaram alta acurácia (Cb de 0,97 e 0,95 para CC<5 e CC>5, respectivamente) e o erro aleatório do QMEP foi de 99,8 e 99,9% para CC<5 e CC>5, respectivamente. A análise “bootstrap” indicou um baixo viés para todos os parâmetros estimados em ambas as equações. A precisão das equações foi moderada, com valores de r2 de 0,61 e 0,52 e valores de ρ de 0,78 e 0,72 para CC<5 e CC>5, respectivamente. Conclui-se que a utilização de leite ou sucedâneo como alimento líquido não afeta o CC, ou o desenvolvimento do CC ao longo do tempo, o qual aumenta exponencialmente de acordo com a idade do bezerro. O CC foi negativamente afetado pelo CL e, por esta razão, diferentes equações são necessárias para estimar o CC de acordo com o CL. O segundo estudo objetivou avaliar a influência de diferentes níveis de proteína não-degradável no rúmen (PNDR) sobre o consumo, desempenho, características de carcaça, balaço de N, desenvolvimento da glândula mamária e o status hormonal de novilhas Holandesas em diferentes estágios fisiológicos (EF). Foram utilizadas 16 novilhas pré-puberes (PRE), com peso corporal inicial de 106±7,6 kg e 4±0,46 meses de idade, bem como 16 novilhas púberes (PUB), com peso corporal inicial de 224±7,9 kg e 12±0,45 meses de idade. O experimento teve uma duração de 84 dias e foi conduzido segundo um delineamento inteiramente casualizado, segundo um esquema fatorial 4×2, com 4 níveis de PNDR na proteína total da dieta ((38, 44, 51 e 57%) e animais em duas idades diferentes (pré-puberes e púberes). Entre os dias 36 e 40 e os dias 78 e 82 os animais foram submetidos à ensaios de digestibilidade com coleta de alimentos, sobras e coletas “spot” de fezes e urina. No dia 0 (imediatamente antes do início do experimento) e dia 83 foram tomadas imagens de ultrassom na área lombar dos animais. Nos dias 0, 21, 42, 63 e 84 foram tomadas imagens de ultrassom da glândula mamaria. E, por fim, nos dias 0 e 84 foram tomadas amostras de sangue para estimar as concentrações séricas de progesterona, estrógeno, IGF-I e insulina. O EF afetou a digestibilidade aparente da MS, e novilhas PRE apresentaram menores valores. Novilhas PRE também apresentaram consumo preferencial por fibra em detergente neutro corrigida para cinzas e proteína (FDNcp) e atividade de seleção contra a proteína bruta (PB) maior que novilhas PUB. O ganho médio diário (GMD) e a retenção de N foram afetados pelo EF, e novilhas PRE apresentaram um GMD de 505 g/dia, enquanto novilhas PUB apresentaram um valor médio de 905 g/dia. Adicionalmente, estas variáveis foram afetadas pelo nível de PNDR, e maiores valores foram obtidos para o tratamento com 51% de PNDR. A análise de pixels na glândula mamária apontou efeito do EF, e novilhas PRE apresentaram maiores valores de pixel. As mensurações iniciais de progesterona sérica demonstraram que as novilhas PRE e PUB mantiveram seu EF durante o experimento. A concentração de IGF-I foi afetada somente pelo EF, e novilhas PUB apresentaram maiores valores. A concentração de insulina não foi afetada pelo EF, mas apresentou uma tendência de ser maior para os tratamentos com 51% de PNDR. Conclui-se que o nível dietético de 51% de PNDR é responsável por aumentar o desempenho de novilhas PRE e PUB. Adicionalmente, novilhas PRE tem menor habilidade de seleção, o que afeta, negativamente, a sua digestibilidade e desempenho. Finalmente, estes animais são mais propensos a ter uma maior proporção de gordura na glândula mamaria, mesmo sob moderadas taxas de crescimento. O terceiro estudo foi conduzido com o objetivo de avaliar de níveis crescentes de PNDR sobre o consumo, as digestibilidade parciais e total, a cinética e as características ruminais, bem como a utilização do N de novilhas leiteiras holandesas. Foram utilizadas 8 novilhas holandesas fistuladas no rúmen, com peso corporal inicial de 276±8,3, em delineamento em quadrado latino 4×4 duplo, com quatro níveis de PNDR na proteína dietética, como segue: 38% de PNDR (38PNDR); 44% de PNDR (44PNDR); 51% de PNDR (51PNDR) e 57% de PNDR (57PNDR). O experimento teve duração de 84 dias, subdivididos em 4 períodos experimentais de 21 dias (14 dias de adaptação + 7 dias de coletas). Foram realizadas 8 coletas “spot” de fezes, urina, conteúdo ruminal e digesta omasal, com intervalo de 8 horas entre cada coleta, como segue: no 15o dia as amostras foram coletadas as 0600h e 1500h; no 16o dia as amostras foram coletadas as 0000h, 0900h e 1800h; e no 17o dia as amostras foram coletadas as 0300h, 1200h e 2100h. No 19o dia foi realizado esvaziamento completo do rúmen 4 horas após a alimentação matutina e no 21o dia o esvaziamento foi realizado imediatamente antes da alimentação matutina. O consumo diário de MS, matéria orgânica (MO), PB, FDNcp e FDNcp potencialmente digestível (pdFDNcp) não foi afetado pelos níveis de PNDR. Adicionalmente, o consumo relativo (g/kg de peso corporal) de MS, PB e FDNcp, assim como o fluxo ruminal de MS, MO, PB, FDNcp pdFDNcp não foram afetados pelos níveis de PNDR. A digestibilidade total da MS, MO, PB, FDNcp e pdFDNcp, bem como as digestibilidade ruminal e intestinal da MS, MO, FDNcp e pdFDNcp não foram afetados pelos níveis de PNDR. No entanto, as digestibilidade ruminal e intestinal da PB apresentaram uma tendência de decréscimo de acordo com o aumento nos níveis de PNDR. Não foram observados efeitos dos níveis de PNDR sobre as taxas de ingestão, passagem e digestão, assim como sobre a concentração de ácidos graxos voláteis. O tratamento 38PNDR apresentou maior concentração de nitrogênio amoniacal ruminal em relação aos outros tratamentos. A excreção de nitrogênio urinário apresentou tendência de queda de acordo com o aumento nos níveis de PNDR. Adicionalmente, o nitrogênio retido apresentou tendência de aumento de acordo com o aumento nos níveis de PNDR e foi maior para os tratamentos 51PNDR e 57PNDR. A síntese de proteína bruta microbiana, a eficiência de síntese de proteína microbiana (PBmic) e a eficiência de uso do nitrogênio para síntese de proteína microbiana diminuíram de acordo com o aumento nos níveis de PNDR na dieta. O fluxo de PNDR aumentou, enquanto a quantidade de proteína degradável no rúmen decresceu de acordo com o aumento nos níveis de PNDR. Adicionalmente, o fluxo de proteína metabolizável apresentou tendência de aumento de acordo com o aumento nos níveis de PNDR e maiores valores foram observados para os tratamentos 51PNDR e 57PNDR. Conclui-se que a digestibilidade intestinal da PB é negativamente afetada pelos níveis de PNDR, o que é proporcionado pela redução no fluxo de PBmic, sendo que esta, provavelmente, digestibilidade intestinal da proteína maior que os alimentos. A excreção urinária de N diminui à medida que a PNDR dietética aumenta, o que é proporcionado pela queda nas perdas ruminais de nitrogênio na forma de amônia e pelo aumento na reciclagem de nitrogênio para o rúmen. A redução na excreção urinaria de nitrogênio, aliada ao aumento no fluxo de proteína metabolizável, o qual foi promovida pelo aumento no fluxo de PNDR ao intestino delgado, são determinantes para promover aumentos na retenção de nitrogênio, o que ocorreu nos tratamentos 51PNDR e 57PNDR.<br>This work was developed from three studies. Therefore, the objective of the first study was to identify variables that influence starter feed intake (SFI), and to develop equations to predict SFI in milk-fed dairy calves up to 64 days of age. The database was composed of individual data of 189 calves from 8 experiments, totaling 6,426 daily observations of intake. The information collected from the studies were: birth body weight (birth BW; kg), SFI (kg/day), fluid milk or milk replacer intake (MI; L/day), sex (male or female), breed (Holstein or Holstein×Gyr crossbred), and age (days). A correlation between SFI and the quantitative variables MI, birth BW, metabolic birth BW (birth BW 0.75), and age was established. Subsequently, data were graphed and based on a visual appraisal of the pattern of the data; an exponential function was chosen. The data were evaluated using a meta-analysis approach to estimate fixed and random effects of the experiments using nonlinear mixed coefficients statistical models. Cross-validation was used to estimate the accuracy and precision of the developed equations using the mean square error of prediction (MSEP), concordance correlation coefficient, which was decomposed into accuracy (Cb) and precision (ρ) parameters, and the coefficient of determination (r 2) as a proxy for precision. In addition, a bootstrap analysis was used to estimate the bias associated with each parameter of the developed equation structure. A negative correlation between SFI and MI was observed (r = –0.388), but age had a positive correlation with SFI (r =0.66). No effect of liquid feed source (milk or milk replacer) was observed in developing the equation. However, 2 equations, significantly different for all parameters, were fit to predict SFI for calves that consume less than 5 (SFI<5) or more than 5 (SFI>5) L/day of milk or milk replacer: SFI<5 = 0.1839±0.0581 ×MI×exp((-0.0040±0.0011× MI + 0.0333 ±0.0021) × (A- (6.0332 × MI + 0.8302±)))±0.35830.5092 - (0.12 × MI); CC>5 = 0.1225±0.0005 × MI × exp((-0.0015±0.0001 × MI + 0.0217±0.0006) × (A- (1.9508±0.1710 × MI + 3.5382±1.3140))) - (0.12 × MI); whereSFI<5 and SFI>5 = starter feed intake prediction for calves that consume less than 5 and more than 5 L/day of milk or milk replacer, respectively (kg/d); MI = milk or milk replacer intake (L/d) and A = age (days). These equations had high accuracy (Cb of 0.97 and 0.95, respectively) and the random errors of MSEP were 99.8 and 99.9% for SFI<5 and SFI>5 equations, respectively. Small biases were observed with the bootstrap analyses for all estimated parameters. The equations’ precision was moderate, with r 2 values of 0.61 and 0.52 and ρ values of 0.78 and 0.72 for SFI<5 and SFI>5, respectively. In conclusion, the use of milk or milk replacer as liquid feed did not affect SFI, or development of SFI over time, which increased exponentially with calf age. Starter feed intake was negatively affected by MI and, and for this reason, different equations are necessary to predict calf SFI according to MI. The second study aimed to evaluate the influence of different levels of rumen undegradable protein (RUP) on intake, performance, carcass characteristics, N balance, mammary gland development and hormonal status of Holstein heifers at different physiological stage (PS). Sixteen prepubertal (PRE) heifers with 106±7.6 kg of initial body weight and aged 4±0.46 months old, as well as, 16 pubertal (PUB) heifers with 224±7.9 kg of initial body weight and aged 12±0.45 months old were used. The experiment was carried out during 84 days following a complete randomized design, in a 4×2 factorial arrangement, with four levels of RUP in dietary protein (38, 44, 51, and 57%), and animals at two PS (prepubertal or pubertal). Between days 36 and 40 and between days 78 and 82 the animals were subjected to digestibility trials with collections of feeds, orts and spot collections of feces and urine. At days 0 (immediately before the beginning of the experiment) and 83 body ultrasound images were taken at the rib area. At days 0, 21, 42, 63 and 84 images of the mammary gland were taken via ultrasound. Finally, at days 0 and 84 blood samples were taken to estimate serum concentration of progesterone, estrogen, IGF-I and insulin. The PS affected the apparent digestibility of DM, and PRE heifers presented lower values. The PRE heifers also presented a preferential consumption for neutral detergent fiber corrected for ash and protein (NDFap) and sorting activity against CP greater than PUB heifers. The average daily gain (ADG) and N retention were affected by PS, and PRE heifers presented an ADG of 505 g/d, while PUB heifers presented an average value of 905 g/d. In addition, these variables were affected by RUP levels, where greater values were obtained for treatments with 51% of RUP. The analysis of pixels in mammary gland images pointed effects of PS, and PRE heifers presented greater pixels values. The initial and final measurements of serum progesterone demonstrated that PRE and PUB heifers kept their PS during the experiment. The IGF-I concentration was only affected by PS, and PUB heifers presented greater values. In addition, insulin was not affected by PS, but presented a tendency to be greater at treatments with 51% of RUP. In conclusion, the dietary level of 51% of RUP is responsible to increase the performance of PRE and PUB Holstein heifers. In addition, PRE heifers have lower sorting ability, what affected, negatively, their digestibility and performance. Finally, these animals are more likely to have greater fat proportion in the mammary gland, even under moderate rates of growth. The third study aimed to evaluate the influence of increasing levels of RUP on intake, total and partial digestibilities, rumen kinetics and characteristics, as well the N use of dairy Holstein heifers. Eight rumen-cannulated Holstein heifers, with an average initial body weight of 276±8.3 were used in a double 4×4 Latin Square design with four levels of RUP in the total dietary protein, as follows: 38% of RUP (38RUP); 44% of RUP (44RUP); 51% of RUP (51RUP) and 57% of RUP (57RUP). The experiment was carried out during 84 days subdivided into 4 experimental periods of 21 d (14 d for adaptation + 7 d for collections). Eight spot collections of feces, urine, ruminal content and omasal digesta were performed with 9 hours interval between each collection, as follows: on 15th d samples were collected at 0600 h and 1500 h; on 16th day samples were collected at 0000 h, 0900 h and 1800 h; on 17th d samples were collected at 0300 h, 1200 h and 2100 h. On 19th d a complete rumen evacuation was performed, 4 hours after the morning feeding and on 21st d immediately before morning feeding. Daily intake of DM, organic matter (OM), CP, NDFap and potential digestible NDFap (pdNDFap) were not affected by RUP levels. In addition, the relative intake (g/kg of body weight) of DM, CP and NDFap, as well as the ruminal outflow of DM, OM, CP, NDFap and pdNDFap were not affected by RUP levels. Total digestibility of DM, OM, CP, NDFap and pdNDFap, as well as ruminal and intestinal digestibilities of DM, OM, NDFap and pdNDFap were not affected by RUP levels. However, ruminal and intestinal digestibilities of CP presented a tendency to decrease according to RUP supply increase. Effects of RUP levels were not observed on the ingestion, passage and digestion rates, as well on the total volatile fatty acid concentration. Treatment 38RUP presented greater concentration of rumen ammonia nitrogen in relation to the other treatments. The urinary N excretion presented a tendency to decrease according to RUP supply increase. In addition, retained N presented a tendency to increase according to RUP levels and greater values were observed for treatments 51RUP and 57RUP. Microbial crude protein (CPmic) synthesis, microbial efficiency and the efficiency of use of N for microbial synthesis, decrease as the supplied RUP increases. Flow of RUP increased, while the amounts of rumen degradable protein decrease according to RUP supply increase. In addition, the flow of metabolizable protein presented a tendency to increase and greater values were observed for treatments 51RUP and 57RUP. In conclusion, the intestinal digestibility of CP is negatively affected by RUPvlevels, what is due to the reduction in the CPmic flow, which, probably, has greater intestinal digestibility than protein of feedstuffs. The urinary N excretion decrease according to RUP supply increase, what is due to the decrease in ruminal N losses as ammonia and the increase in N recycling. The reduction in the urinary N excretion allied to increases in the flow of metabolizable protein, which are promoted by increases in the flow of RUP to the small intestine, are determinant to promote increases in the retained N, which occurred for treatments 51RUP and 57RUP.

Yearly calvings are essential to the sustainability of modern dairy farming. Currently, calving difficulty (or dystocia) affects one in six calvings among UK dairy herds but vary from 2 to 50% internationally. In dairy cows, despite reports of impaired performance, the extent and threshold of the effect of dystocia on health and performance remains unclear. Over the past years, there has also been increasing concerns about the levels of pain experienced by the dystocial cows. Better understanding of their parturition progress and behaviours is needed so that informed decisions on pain mitigation can be taken. Additionally, the impact of dystocia (besides stillbirth) should also be addressed in dairy calves. The objective of this study was to address the effects of a difficult calving on the health and welfare of both dairy cows and calves. Retrospective analyses of an experimental farm’s detailed records were used to relate calving difficulty with health and performance of the dairy cow. The results showed that after any difficulty at calving, dairy producers incur long-lasting shortfalls in milk sales. Dystocial cows also have impaired fertility, are more likely to leave the herd early and have a higher risk of dystocia at the following calving, thus there is a long-term detrimental impact on dystocial cows. Video monitoring of calvings allowed detailed investigation of the parturition progress and behaviours of dystocial Holstein cows giving birth to singleton liveborn calves. The study of calving behaviours and parturition progress indicated longer later stages of parturition, increased restlessness and tail raising in the six hours preceding expulsion of the calf, for dystocial cows receiving farm assistance compared with cows calving unaided. This may relate to the expression of higher levels of pain when dystocia occurs. The onset of maternal behaviour was not delayed following calving difficulty, and firm conclusions could not be drawn from investigation of some behavioural indicators of pain in the first three hours postpartum. Experimental work allowed the monitoring of a cohort of 496 calves born with various degrees of birth difficulty over two years. All but one vet assisted calves were born dead, and farmer assisted calves were more likely to be stillborn than calves born without assistance. Stillborn dystocial calves displayed larger internal damage, than stillborn eutocial calves, but they did not have a different body shape at birth than dystocial calves that survived. Dystocial dairy calves that survived the birth process had lower vigour at birth, had higher salivary cortisol, acquired lower passive immunity and received more health treatments in the neonatal period. Dystocial heifers also had higher mortality rates by weaning but had similar growth to first service. Historical records from the farm also showed that dystocial heifer calves were three times more likely to have died by weaning and by first service than calves born without assistance. For those who survived, there was, however, no indication of altered growth to weaning or subsequent impaired fertility. This may be explained by the early mortality of the most badly affected calves or by farm management. However, their high mortality rates still raise welfare concerns. Altogether, results suggest that dairy calves born with any difficulty have poorer welfare in the neonatal period and possibly beyond. The experience of any calving difficulty in dairy cattle therefore not only impairs the welfare of the cow, but also the welfare from their resulting calf. Any strategy implemented to lower the occurrence and mitigate the effects of dystocia will therefore improve the welfare of the cows, their calves and enhance the farm’s economic sustainability.

Master of Science<br>Department of Animal Science and Industry<br>L.N. Edwards-Callaway<br>This thesis includes two studies that assessed pain responses to husbandry procedures in order develop mitigation tools. The objective of the first trial was to identify method-related differences in behavioral pain responses in calves of two ages (6 week and 6 months) subjected to castration: surgical cut (CP; n=18), surgical cut and emasculator (CC; n=20), rubber banding (BAND; n=18), or control manipulation of the scrotum (CONT; n=20). Behavior was evaluated pre- and post-castration to record foot stamps, tail flicks, kicks, elimination, in addition to standing and lying post-castration. For 6 week calves, the probability of kicking and eliminations was greater for surgical castrates and all castrated animals, respectively. The probability of kicking was greatest for all 6 month castrates while BAND and CONT had greater probability of elimination. Both age groups increased standing post-castration. Lying decreased in 6 week calves but was unchanged for 6 month calves. Six week calves displayed more tail flicks and tended to display less foot stamps than 6 month calves. Six week calves showed a decrease in tail flicks and foot stamps in response to castration while 6 month calves showed an increase in both behaviors. CP and CC, but not BAND, resulted in less tail flicks than CONT post castration. The second trial compared the effects of preemptive analgesics administered to calves subjected to dehorning with local anesthesia. Six month Holstein steers were randomly assigned to receive one of the following treatments (n= 8/group): meloxicam (1 mg/kg PO), gabapentin (15mg/kg PO), meloxicam (1 mg/kg) and gabapentin (15 mg/kg) PO, flunixin (2.2 mg/kg IV), or a placebo. Drug, cortisol, ex-vivo prostaglandin, haptoglobin, and substance P concentrations, ocular thermography, algometry, and average daily gain were evaluated. Analgesic-treated calves had lower plasma SP concentrations and improved ADG compared with controls. Flunixin calves had reduced cortisol and ex-vivo prostaglandin concentrations for 24h compared to controls. Meloxicam treated calves showed an increase in MNT at two horn bud sites compared with the other treatments. Overall, the results provide validation of responses to noxious stimuli that can be used to develop pain alleviation for livestock.

Current data indicates that feeding dairy calves more nutrients in early life allows them to produce more milk in the future. Mechanisms responsible are poorly understood. Thirty-six Holstein heifer calves were fed either a restricted (R; 20.2% crude protein [CP], 19.8% fat, dry matter (DM) basis, fed at 0.44 kg/hd/d, DM basis) or an enhanced (EH; 28.9% CP, 26.2% fat, DM basis, fed at 1.08 kg/hd/day, DM basis) milk replacer (MR) and given either a placebo or estradiol (E2) implant to assess differential responses to E2. Our underlying hypothesis was that calves fed more nutrients are better able to respond to mammogenic stimuli and will have a more developed mammary gland as a result of imposed treatments. Enhanced-fed calves grew at a faster rate, were heavier at weaning, and had more functional mammary tissue (i. e., parenchyma; PAR) mass in the mammary gland at weaning (7.3-fold). Additionally, biochemical composition of the PAR was not impacted by the dietary treatments imposed. Furthermore, EH-fed calves had an increase in the number of actively dividing cells throughout the mammary PAR as well as increased intensity of estrogen receptor expression in the population of cells expressing the estrogen receptor. Enhanced-fed calves had an up-regulation of genes and pathways in the PAR related to metabolism, cellular signaling, and cellular growth. When given E2, EH-fed calves experienced the greatest overall mammary gland development and had the greatest PAR mass without compromised composition. When comparing EH- and R-fed calves given E2, differential expression of genes and pathways related to cell growth, cell signaling, and metabolism was observed. In summary, data indicates that enhanced feeding of calves in early life allows increased responsiveness to mammogenic stimuli and a corresponding increase in mammary development. We suggest that this may at least partly explain the improved future milk production in calves fed in this manner.<br>Ph. D.

In their first days of life, dairy calves in artificial rearing systems often have difficulty using an artificial teat for feeding. I examined the age at which calves are able to stand up and suckle without lifting assistance, as well as their suckling behavior when presented with a plain dry teat versus a dry teat modified with a presumably attractive odor or taste substance. Single-housed newborn dairy calves (n = 51) were presented for ten consecutive days with a two-minute two-choice test, in which suckling time was recorded for 1) a plain (control) teat vs. a glucose-coated teat (taste test) and 2) a plain teat vs. a teat with a "Freshly Cut Grass" odor (odor test). On average, the calves were able to suckle without lifting assistance from the second or third day of age on. The "Freshly Cut Grass" odor had no significant effect on their suckling behavior. The calves showed a significant preference for suckling the glucose-coated teat and displayed a significantly longer total suckling time in the taste test compared to the odor test. There were no significant differences between sexes regarding suckling preference. The results of the present study show that glucose had a significant effect on the calves' teat preference and significantly increased total suckling time with a dry artificial teat. As such, glucose may increase suckling motivation in non-efficient drinkers or ill calves with low motivation to suckle.

Dissertação de Mestrado Integrado em Medicina Veterinária<br>O vitelo recém-nascido apresenta um sistema imunitário imaturo e por conseguinte uma maior vulnerabilidade aos agentes patogénicos. O colostro serve de meio para a transferência de imunoglobulinas (Ig) maternas, que vão levar a um reforço do sistema imunitário do neonato. Por sua vez, esta transferência da imunidade passiva (TIP) vai contribuir para a diminuição da morbilidade e mortalidade nestes animais. Tendo isto em consideração, o principal objetivo deste estudo foi avaliar a qualidade dos colostros e a imunidade dos vitelos e assim identificar fatores que influenciam a concentração de Ig no colostro e no sangue dos vitelos e a ocorrência de doença neonatal nas explorações. Além disso, fez-se a caracterização das explorações aderentes ao estudo e das suas práticas de maneio e também compararam-se dois grupos de explorações diferentes. Participaram no estudo 33 explorações com 126 pares progenitora-cria, estas vacarias apresentavam um efetivo médio de 161 animais, onde predominava a raça Holstein-Frísia (HF). Na sua grande maioria não existia banco de colostro, praticava-se um período de secagem igual ou superior a 60 dias, o tipo de alimentação mais prevalente neste período era um misto de erva fresca e silagem de milho e/ou erva e os partos ocorriam maioritariamente na pastagem. A maioria dos produtores desinfetava o umbigo dos vitelos, administrava 2 a 3 L de colostro através de balde com tetina, biberão ou sonda, sendo que todos faziam esta administração preferencialmente até às 8 h de vida, separava-os das progenitoras antes das 12 h de vida e alojava-os no interior de instalações. A média das contagens de células somáticas (CCS) destas explorações foi de 183,370 células/mL, na maioria dos casos o leite de desperdício era incluído na dieta dos vitelos. A maioria das amostras de colostro foi avaliada como sendo de boa qualidade (58,62%) e em termos de imunidade, a maioria dos vitelos não apresentou falha na TIP (FTIP) (58,62%). O estudo não encontrou diferenças entre os dois grupos de explorações e nenhum dos fatores em estudo, cujo efeito foi avaliado na qualidade do colostro e na ocorrência de doença neonatal, apresentou uma associação estatisticamente significativa. Já para a imunidade dos vitelos, os fatores concentração de Ig no colostro e a altura da toma de colostro apresentaram um efeito significativo, o que veio realçar a sua importância para uma TIP bem-sucedida.<br>ABSTRACT - Effect of colostrum management on calves’ immunity on dairy farms from São Miguel - The new born calf presents an immature immune system, hence a bigger vulnerability to pathogens. In this way, colostrum serves as a mean of transference for maternal immunoglobulins (Ig), leading to a reinforcement of the neonate’s immune system. This transfer of passive immunity (TIP) will contribute for a decrease in morbidity and mortality in these animals. Having that in mind, the main goal of this study was to evaluate the colostrum’s quality and calves’ immunity and thereby identify the factors that influence the Ig concentration in colostrum and in calves’ blood and the occurrence of neonatal disease at the farms. Besides that, a characterization of the farms that participated and their management practices was done and also a comparison between two different groups of farms. Thirty three farms with 126 dam-calf pairs participated in the study. These farms presented a mean herd size of 161 animals, where the breed Holstein-Friesian (HF) was predominant. In their majority, there was no colostrum bank, the dry period was equal to or higher than 60 days, the most common type of feed was a mix of pasture and grass and/or corn silage and the parturition occurred mainly at pasture. The majority of the farmers disinfected de calves’ navel, provided 2 to 3 L of colostrum through nipple bucket, nipple bottle or oesophageal tube feeder, all of them provided the colostrum preferably until 8 h of calves’ life, separated the calves from the dam before 12 h of life and housed them. The somatic cell counts’ (CCS) mean of these farms was 183,370 cells/mL, in the majority of the cases farmers included waste milk in the calves’ diet. The majority of colostrum samples were graded as high quality (58,62%) and in terms of immunity, most calves did not show a TIP failure (FTIP) (58,62%). The study did not find differences between the two groups of farms. Also, none of the factors studied, influencing colostrum quality or the occurrence of neonatal disease, showed a statistically significant effect. Regarding calves’ immunity, the factors, colostrum’s Ig concentration and the moment of the colostrum intake, showed a significant effect, which highlights their importance for a successful TIP.<br>N/A

Dissertação de Mestrado Integrado em Medicina Veterinária<br>Mortalidade Peri-natal (MP) em vitelos tem aumentado a nível internacional. A definição de MP varia consoante o estudo, mas geralmente pode ser definida como a morte do vitelo antes, durante ou até 48 horas após o parto, depois de decorrida uma gestação de pelo menos 260 dias. O objectivo deste estudo foi, numa primeira fase, determinar: a prevalência de MP em seis explorações leiteiras em Portugal, quais os factores de risco que lhe estão associados e quais as medidas que se devem implementar para minimizá-la. Nesse sentido, foram analisados 4537 registos de animais pertencentes às raças Holstein-Frísia, Montbeliarde e Vermelha Sueca nascidos durante o ano de 2008 e de 2009. A prevalência de MP no total das explorações foi de 20% e a incidência de mortalidade após as 48 horas de vida foi de 9,9%. Numa segunda fase, determinaram-se os factores por exploração que tiveram influência na sobrevivência/mortalidade das fêmeas até às 48 horas e até aos 9 meses de idade. Na primeira fase, a sobrevivência/mortalidade dos vitelos foi analisada com um modelo de regressão logística em dois momentos (mortalidade até às 24 horas após o parto e mortalidade entre as 24 e as 48 horas após o parto) e relacionados com os seguintes factores de risco: exploração, mês de nascimento, sexo, raça, paridade da mãe, nascimento em dia não útil/ dia útil e “tipo de parto” (simples, duplo ou triplo). Em 2008 e 2009, o risco de Mortalidade Peri-natal foi maior no mês de Dezembro, na exploração E4, em machos, em crias de primíparas e em recém-nascidos resultantes de partos duplos. Na segunda fase, a sobrevivência/mortalidade das fêmeas em cada exploração foi analisada com um teste de independência de qui-quadrado. Em 2008 e 2009 o “tipo de parto”, a paridade da progenitora e o mês de nascimento influenciaram significativamente a mortalidade das fêmeas até aos 9 meses em algumas explorações. Estes resultados podem ser minimizados, num futuro próximo, através de um melhoramento no maneio das explorações, na supervisão adequada dos partos, de cuidados imediatos ao nascimento e de uma atenção reforçada aquando de partos em épocas do ano mais rigorosas. Assim, a incidência de MP diminuirá e estará garantido o bem-estar das crias e ainda, poderá certificar-se que esses animais serão as futuras reprodutoras da exploração de leite.<br>ABSTRACT - Perinatal Mortality in calves - Calves Perinatal Mortality (PM) has increased all over the world during the last decades. Its definition is not clear and it varies among different studies on the subject. However it can be generally understood as the calves’ death before, during or until 48h hours after calving, following a gestation period of at least 260 days. The initial goals of this study were: to find out what was the prevalence of PM in 6 Portuguese dairy farms, which risk factors were associated to it and which preventive measures can be taken to diminish this incidence. 4537 records of Holstein-Friesian, Monbelliarde and Sweedish Red calves born during 2008 and 2009 were analyzed. PM prevalence was 20% and the incidence of mortality after that period was 9,9%. During a second approach of the study, it was determined which factors in each farm influenced the survival/mortality of female calves until forty-eight hours after birth and until they were nine months old. The calve’s survival/mortality was firstly analyzed with a logistic regression model in two moments (mortality until 24h after birth and mortality between the 24 and 48 hours that followed birth) considering the following risk factors: farm, month of birth, gender, breed, parity of dam, day of birth (working day/non working day) and twin status. During 2008 and 2009, the risk factors that were associated with a higher PM were: the month of December, farm E4, male calves, heifer calving and twin calving. Secondly the survival/mortality of females in each farm was analyzed with the qui-square independent test. It was concluded that during 2008 and 2009 the twin status, the parity of dam and the month of birth influenced significantly the female’s mortality until their nine months old in some of the farms studied. These results can be improved if a better handling of animals, supervision during calving and immediate care of calves after birth is carried out and also, if a special attention is taken during calving in winter periods. By assuring these simple measures, the incidence of PM will decrease and new-born calves will have their welfare guaranteed, improving the chances of becoming excellent reproductive animals.