Influence of Cottonseed Meal Supplementation on Voluntary Intake, Rumen Fermentation and Rate of Passage of Prairie Hay in Beef Steers2

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Abstract
Eight rumen-cannulated steers (average weight of 214 kg) fed prairie hay ad libitum were used in a crossover design. Treatments were no supplement or 800 g of cottonseed meal±head−1±d−1. Voluntary intake of hay was measured the last 10 d of each 28-d period. Rumen samples were withdrawn at −3, 0, 1, 3, 6, 9 and 21 h postsupplement on d 22 of each period to measure fluid dilution rate (cobalt ethylenediaminetetracetate) and fermentation characteristics. An intraluminal dose of Yb-labeled hay followed by fecal sampling on d 23 through 28 of each period was used to measure particulate passage rate. In vitro dry matter disappearance (IVDMD) of hay at various incubation times was measured with inoculum from each treatment group. Rumen pH and total volatile fatty acid concentrations did not differ (P>.10) between treatments. Cottonseed meal-supplemented steers had higher (P<.05) rumen ammonia levels at all sampling times. Molar proportion of acetate was higher at −3, 0 (P<.05), 1, 3, 6 (P<.01) and 9 h (P<.10) in control than in supplemented steers and molar proportion of propionate was higher in supplemented steers at −3 (P<.05), 0 (P<.10) and 6 h (P<.01) after supplementation. In vitro rate of dry matter disappearance did not differ (P> .10) for supplemented (4.5%/h) compared with control inoculum (3.9%/h), but IVDMD was greater for supplemented inoculum at the 6-(P<.10), 12- (P<.05), 18- (P<.10) and 24-h (P<.025) incubation periods. Rumen fluid volume did not differ (P>.10) between treatments; however, supplemented steers (2.8 liters/h) had a greater (P<.05) fluid outflow rate than did control steers (2.2 liters/h). Prairie hay intake was increased (P<.01) by cotton-seed meal supplementation (16.9 vs 21.5 g/kg body weight). Particulate dilution rate was faster (P<.01; 2.9 vs 4.5%/h) and total mean retention time shorter (P<.01; 54.9 vs 75.8 h) in supplemented compared with control steers. Copyright © 1985. American Society of Animal Science . Copyright 1985 by American Society of Animal Science

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