Literatura académica sobre el tema "Elk – Oregon – Food"

ABSTRACT The 16S rRNA sequences and selected phenotypic characteristics were determined for six recently isolated bacteria that can tolerate high levels of hydrolyzable and condensed tannins. Bacteria were isolated from the ruminal contents of animals in different geographic locations, including Sardinian sheep (Ovis aries), Honduran and Colombian goats (Capra hircus), white-tail deer (Odocoileus virginianus) from upstate New York, and Rocky Mountain elk (Cervus elaphus nelsoni) from Oregon. Nearly complete sequences of the small-subunit rRNA genes, which were obtained by PCR amplification, cloning, and sequencing, were used for phylogenetic characterization. Comparisons of the 16S rRNA of the six isolates showed that four of the isolates were members of the genusStreptococcus and were most closely related to ruminal strains of Streptococcus bovis and the recently described organism Streptococcus gallolyticus. One of the other isolates, a gram-positive rod, clustered with the clostridia in the low-G+C-content group of gram-positive bacteria. The sixth isolate, a gram-negative rod, was a member of the familyEnterobacteriaceae in the gamma subdivision of the classProteobacteria. None of the 16S rRNA sequences of the tannin-tolerant bacteria examined was identical to the sequence of any previously described microorganism or to the sequence of any of the other organisms examined in this study. Three phylogenetically distinct groups of ruminal bacteria were isolated from four species of ruminants in Europe, North America, and South America. The presence of tannin-tolerant bacteria is not restricted by climate, geography, or host animal, although attempts to isolate tannin-tolerant bacteria from cows on low-tannin diets failed.

Hydrogen sulfide (H2S) is a recently described gaseous vasodilator produced within the vasculature by the enzymes cystathionine γ-lyase and 3-mercaptopyruvate sulfurtransferase. Previous data demonstrate that endothelial cells (EC) are the source of endogenous H2S production and are required for H2S-induced dilation. However, the signal transduction pathway activated by H2S within EC has not been elucidated. TRPV4 and large-conductance Ca2+-activated K channels (BK channels) are expressed in EC. H2S-induced dilation is inhibited by luminal administration of iberiotoxin and disruption of the endothelium. Calcium influx through TRPV4 may activate these endothelial BK channels (eBK). We hypothesized that H2S-mediated vasodilation involves activation of TRPV4 within the endothelium. In pressurized, phenylephrine-constricted mesenteric arteries, H2S elicited a dose-dependent vasodilation blocked by inhibition of TRPV4 channels (GSK2193874A, 300 nM). H2S (1 μM) increased TRPV4-dependent (1.8-fold) localized calcium events in EC of pressurized arteries loaded with fluo-4 and Oregon Green. In pressurized EC tubes, H2S (1 μM) and the TRPV4 activator, GSK101679A (30 nM), increased calcium events 1.8- and 1.5-fold, respectively. H2S-induced an iberiotoxin-sensitive outward current measured using whole cell patch-clamp techniques in freshly dispersed EC. H2S increased K+ currents from 10 to 30 pA/pF at +150 mV. Treatment with Na2S increased the level of sulfhydration of TRPV4 channels in aortic ECs. These results demonstrate that H2S-mediated vasodilation involves activation of TRPV4-dependent Ca2+ influx and BK channel activation within EC. Activation of TRPV4 channels appears to cause calcium events that result in the opening of eBK channels, endothelial hyperpolarization, and subsequent vasodilation.

Research was conducted near the Starkey Experimental Forest and Range in northeastern Oregon. Effects of defoliating bluebunch wheatgrass (Agropyron spicatum (Pursh) Scribn. and Smith) to increase the quality of regrowth available on elk (Cervus elaphus nelsoni) winter range were studied from 1988 through 1990. Clipping treatments were implemented to condition the forage regrowth. Treatments were no defoliation, spring defoliation (7.6 cm stubble height) in June, and fall defoliation (7.6 cm stubble height) in September. Percent calcium, phosphorus, in vitro dry matter digestibility (IVDMD), and available forage (kg/ha DM) of regrowth present on control, spring defoliated, and fall defoliated plots were determined in November and April of both years. Conditioned forage that was again defoliated in the winter was also analyzed for nutrient quality and available forage. Spring conditioning did not affect (p > 0.05) the forage in percent calcium, phosphorus, or available forage, and only slightly increased the IVDMD, when compared to the control in November. In November, the control and spring conditioned forages were deficient in meeting elk requirements for phosphorus, and contained wide calcium to phosphorus ratios. The forages were below 50% IVDMD, and digestible energy levels were below animal requirements in year 1, indicating that spring conditioning did not have an effect on the quality of winter range forage. Defoliation in the vegetative phenology stage allowed the regrowth to complete the growing season similarly as undefoliated plants. Fall conditioning significantly increased the percent phosphorus and IVDMD, while decreasing the available forage compared to the control and spring conditioned forage in November. Fall conditioned forage exceeded elk requirements in both calcium and phosphorus. The calcium to phosphorus ratio was near the optimum absorption range. Digestibility was high, and digestible energy levels were above animal requirements for both years. Fall conditioning however, may create a severe deficit of forage if regrowth is not achieved. In April, there were no differences among treatments in percent calcium, phosphorus, or available forage. Forage from all treatments exceeded elk requirements in calcium and phosphorus, and the calcium to phosphorus ratio would allow optimum absorption of both minerals. Digestibility was high for forage from all treatments. This indicated that the previous years defoliation did not effect forage quality the following spring. Conditioned forage that was again defoliated in the winter was not different in percent calcium or phosphorus when compared to the control in April. Depending on the year and conditioning treatment, there were statistically significant differences in IVDMD and available forage between the control and the winter defoliated samples in April. Conditioned forage that was not defoliated in the winter (April (U)) and winter defoliated samples (April (W)) were comparable in forage quality and available forage in April, though statistical differences were calculated for the spring conditioned samples in year 1, and fall conditioned samples in year 2.
Graduation date: 1992

The effects of late spring defoliation on the winter forage quality of bluebunch wheatgrass (Agropyron spicatum [Pursh] Scribn. & Smith), Idaho fescue (Festuca idahoensis Elmer) and elk sedge (Carex geyeri Boott) and the response of wintering Rocky Mountain elk (Cervus elaphus nelsoni Bailey) to changes in winter range forage quality were examined. The study included two experiments; a hand clipping experiment conducted on bluebunch wheatgrass and a sheep grazing experiment conducted on bluebunch wheatgrass, Idaho fescue, and elk sedge. Four treatments were applied to bluebunch wheatgrass in the clipping experiment: 1) the entire basal area of individual plants was clipped to a 7.6 cm stubble height during the mid boot phenological stage, 2) one-half the basal area of individual plants was clipped to a 7.6 cm stubble height during the mid boot stage, 3) the entire basal area of individual plants was clipped to a 7.6 cm stubble height during the inflorescence emergence stage, and 4) plants were left unclipped as a control. In early November, forage samples from each of the three clipping treatments exhibited increases in percent crude protein and percent in vitro dry matter digestibility compared to the unclipped control treatment. Clipping the entire basal area of bluebunch wheatgrass plants to a 7.6 cm stubble height during the mid boot or inflorescence emergence stage was more detrimental to plant vigor than clipping one-half the plant basal area during the mid boot stage or leaving the plants unclipped. There was some evidence that clipping one-half the plant basal area during the mid boot stage may improve plant vigor compared to no clipping. Differences in crude protein, in vitro dry matter digestibility, and dry matter yield from winter forage samples of bluebunch wheatgrass, Idaho fescue and elk sedge were detected between plots grazed by domestic sheep during the boot stage of bluebunch wheatgrass and plots where sheep grazing was excluded. No differences in winter elk utilization of bluebunch wheatgrass, Idaho fescue, or elk sedge were detected between the late spring sheep grazing treatment and sheep exclusion treatment. Plot occupancy by wintering elk was similar between plots grazed by sheep and plots where sheep grazing was excluded. Although, wintering elk did not appear to respond to the livestock grazing treatment, results from this study suggest small improvements in the winter forage quality of perennial grasses such as bluebunch wheatgrass can result following late spring defoliation. Forage conditioning treatments which produce even small improvements in forage quality may be important to the nutritional status of wintering elk.
Graduation date: 1997

This research was conducted on three study areas on elk winter ranges in Northeast Oregon. One was on the Starkey Experimental Forest and Range and the others were in the same vicinity. Plant appendages, spring and fall defoliation and fall growth of bluebunch wheatgrass were evaluated in terms of quality of nutrient content during September through April of 1986-87 and 1987-88. Four treatments were applied. Plants were clipped to a 2.5 cm and 7.6 cm stubble height in the spring before the boot stage of phenological development; plants were clipped to a 7.6 cm stubble height in the fall after plant maturity in September; plants were not clipped during the year. Percent crude protein, dry matter digestibility (DMD), acid detergent fiber (ADF), and lignin were evaluated monthly. Samples from the four treatments were also analyzed from October to April to determine monthly changes in nutrient contents. Production of growth from all treatments was measured in October and March each year. Leaf material had higher percent crude protein and DMD, with lower percent ADF and lignin than the inflorescence and culm. The third leaf (the youngest plant material) had the highest nutrient value of all appendages. The culm and inflorescence values were not statistically different. Growth following spring defoliation treatments produced higher percent crude protein and DMD (P<.05), with a lower percent ADF and lignin than non-treated plants in both years. This was particularly pronounced during 1986 when precipitation in late summer initiated fall growth. Growth following spring defoliation and bluebunch wheatgrass not defoliated did not produce crude protein or DMD values sufficient to meet minimum dietary maintenance requirements for elk. Fall precipitation adequate to promote fall growth occurred only in 1986. Growth after fall defoliation had the highest percent crude protein and DMD with the lowest ADF and lignin values of all vegetation sampled. However, without 3-5 cm of late summer/early fall rains, fall growth does not occur. This happened in 1987. When growth does occur in fall the quality of the growth exceeds the minimum dietary maintenance requirements for elk. Freezing and thawing of fall growth plant material had minimal effect on forage quality. There were differences (P<.05) between the monthly values for percent crude protein and ADF starting in October and ending in April. However, the percent DMD and lignin from October to April were not different (P<.05).
Graduation date: 1993