Studies were carried out to investigate the effect of dietary amino acid level on apparent ileal amino acid digestibility. Six barrows, average initial BW 35 kg, were fitted with a simple T-cannula at the distal ileum and fed six diets according to a 6 x 6 Latin square design. Six cornstarch-based diets containing six levels of CP from SBM (4, 8, 12, 16, 20, and 24% CP, respectively) were formulated. Chronic oxide was included as a digestibility marker. Each experimental period consisted of 8 d. After a 6-d adaptation period, ileal digesta were collected for 24 h during d 7 and 9 at 2-h intervals. The pigs were fed twice daily, equal amounts, at 0800 and 2000. The dietary allowance was 1,600 g/d during the first period and increased by 100 g each following period. There was a quadratic increase (P < .05) in apparent ileal amino acid digestibility as the dietary CP content was increased from 4 to 24%. Initially, the apparent ileal amino acid digestibilities increased sharply then gradually reached their plateaus, after which there were no further increases and the digestibility values became independent of the dietary amino acid levels. The lower end points of 95% confidence intervals of the plateau ileal digestibility values were defined to be the initial plateau digestibilities. The dietary CP and amino acid contents, corresponding to the initial plateau digestibility values, represent the dietary threshold levels.(ABSTRACT TRUNCATED AT 250 WORDS)
JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Allen Press and Society for Range Management are collaborating with JSTOR to digitize, preserve and extend access to Journal of Range Management. AbstractImpacts of long-term cattle grazing on litter and soil organic matter were assessed in mixed prairie, parkland fescue, and foothills fescue grasslands of Alberta, Canada. Grazing regimes were of light to very heavy intensities, grazed early, late, and continuously during the growing season. Litter and soil organic matter were sampled in 0.1-nM2 quadrats and removed as live vegetation, standing litter, fallen litter, and soil organic matter. Litter and organic matter samples were air dried and sorted by size using sieves and an automatic sieve shaker. Organic carbon content was determined by thermal oxidation. Ground cover was determined using point frames, and heights of standing litter and fallen litter were measured.Heavy intensity and/or early season grazing had greater negative impacts on litter and soil organic matter than did light intensity and/or late season grazing. Under the former regimes there were significant reductions in heights of standing and fallen litter, decreases in live vegetative cover and organic matter mass, and increases in bare ground. More large particle-sized organic matter, particularly standing litter, occurred in controls than in grazed treatments since it would not be removed or trampled by grazing animals. More medium and small particle-sized organic matter occurred in grazed treatments than in ungrazed controls since vegetation likely decomposed more rapidly when it was trampled and broken down as animals grazed.
The effects of alfalfa saponins on ruminal pH and VFA concentrations, protozoal numbers, forestomach motility, and digesta flow from the rumen were examined in this experiment. In a preliminary study, either 800 or 1600 mg/kg of saponins per kg BW were administered intraruminally in a single dose to one of two 60-kg wethers. Ruminal contractions were suppressed within 15 min. The study was terminated when one wether didn't recover. Saponins were then administered intraruminally in two equal doses daily into four ruminally and duodenally cannulated wethers (60 +/- 1 kg) in amounts equivalent to 0, 200, 400, and 800 mg/kg BW daily in a 4 x 4 Latin Square arrangement. Saponins increased VFA concentrations (P = .001) and lowered ruminal pH (P = .001) after 2 d of administration. On d 2 and d 14, saponins decreased (P < .01) protozoal populations. On d 11, pressure changes during ruminal contractions increased by 79% during resting (P = .06), 202% during feeding (P = .05), and 53% during an 8-h period (P = .08) as the level of saponins increased from 0 to 800 mg/kg BW. Administered saponins increased duodenal flows of OM and total N by 19 and 26%, respectively (P = .04 and .01). Apparent total tract N digestibility was reduced (P = .02) by 5% at the highest saponin dosage. We conclude that alfalfa may contain enough saponins to adversely impact ruminoreticular motility. Saponins also caused decreased ruminal protozoal populations, increased flow of total duodenal N, and reduced ruminal and total tract apparent digestibilities.
Four ruminally cannulated Hereford steers (531 +/- 32 kg) without weights (control; C) or with 24-kg weights (W) in the rumen were used in a double crossover design experiment to determine the effects of changes in frequency of reticular contractions at maintenance feed intakes on passage rates of particulate matter and fluid from the rumen. Duration of reticular contractions, apparent digestibilities and heat and methane productions were also determined. Weights in the rumen had no effect (P = .07) on frequency of reticular contractions before feeding; however, frequencies of reticular contractions were higher in C than in W steers during feeding (P = .03) and after feeding (P = .05). Weights in the rumen increased the average duration of contractions before feeding (P = .04), during feeding (P = .01) and after feeding (P = .05) by 12, 15 and 15%, respectively. Fractional outflow rates of ruminal and whole gastrointestinal particulate matter were 38% and 49% lower (P = .001) in C than in W steers, respectively. Weights in the rumen reduced (P = .001) methane production (liters/d) by 29%. Methane production was inversely correlated with fractional outflow rate for ruminal particulate matter (r = -.53; P = .034). Heat productions for W and C steers were 12.3 and 12.6 Mcal/d, respectively. Weights in the rumen had no effect on apparent digestibility. Duration of reticular contractions, in contrast to frequency of contractions, was the important factor influencing passage rates of both ruminal fluid and particulate matter. Methane production was decreased when passage rates were increased.(ABSTRACT TRUNCATED AT 250 WORDS)
The potential contribution of nutritionally induced differences in follicular and oocyte maturity to embryo survival was addressed in pigs. When
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