Academic literature 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