A series of trials was conducted to determine the ruminal degradation of nitrogenous compounds and dry matter of soybean meal, wet brewers grains, and dried brewers grains. In situ and in vitro estimates of degradation were positively correlated but yielded different absolute values for measures of ruminal degradation. Ruminal digestion of protein, predicted from in situ data, was 42, 73, and 83% for brewers dried grains, brewers wet grains, and soybean meal. Drying of wet grains at either 50 or 150 degrees C increased resistance to ruminal digestion equally. Measurements of flow of dry matter and nitrogen of feed origin to the duodenum were made in vivo for diets containing either brewers dried grains or soybean meal. Negative apparent digestibility of nitrogen in the rumen for a 13% crude protein, brewers dried grains ration indicates the potential for using a non-protein nitrogen supplement with this ration. Resistance to digestion of nitrogen from brewers dried grains occurred only in the rumen. Amino acid patterns delivered to the small intestine and digestion of duodenal contents were similar for diets containing brewers dried grains or soybean meal.
Forty four multiparous Holsteins, 114 +/- 28 days in milk (32 kg/day, 3.4% fat), were fed a basal diet of 12% crude protein and 20% acid detergent fiber for 10 days, then stratified by milk production into four groups. Cows were randomized to one of nine diets in a 3 X 3 factorial in which basal was supplemented with dried brewers grains, wet brewers grains, or soybean meal to supply in the diet 14.5, 16.0, and 17.5% crude protein. Eight cows remained on basal during the 50-day trial. Basal contained: 14% alfalfa silage, 27% ensiled ground-corn, 53% corn silage, and 6% vitamin-mineral mix. Milk production (kg/day) for cows fed dried brewers grains (29.4) and wet brewers grains (28.9) was higher than soybean meal (26.2) and basal (23.1). Milk production was different for diets with high (29.6) vs. low (27.8) and medium (27.2) protein. Dry matter intake (as percent of body weight) was 3.7, 3.5, 3.3, and 2.9 for dried brewers, wet brewers, soybean meal, and basal, respectively. Milk protein percent and milk fat percent differed for protein source. Rumen fluid ammonia nitrogen for combined 2, 4, and 6 h post-feeding, was (mg/100 ml) 10.4 for dried brewers, 14.9 for wet brewers, and 18.0 for soybean meal and increased from 13.2 to 15.4 with increased protein. Plasma urea tended to follow patterns of rumen ammonia. Dried brewers grains had lower apparent nitrogen digestibility but equal nitrogen balance, indicating more efficient metabolic use than soybean meal.
Twenty-four first-lactation cows, averaging 82 d postpartum, were protein depleted for 20 d by consuming a 9.4% crude protein diet. The cows were then assigned randomly and equally to a 2 X 3 factorial arrangement of dietary treatments in which either pelleted or unpelleted soybean meal containing 1% sodium bentonite was supplemented to corn or corn silage-based diets to yield 12.2, 15.4, or 18.1% crude protein, dry basis. Between 9 and 15 d of the depletion period, milk, milk protein production, and dry matter consumption decreased 20 to 25%. Blood hematocrit increased. On refeeding three amounts of protein, dry matter intake was greatest during week 4 of repletion. Milk production rapidly increased to a plateau averaging approximately 88% of preexperimental production with a somewhat greater response to the higher soybean rations. Neither intake, milk, milk protein production, plasma urea, serum albumin, or blood hematocrit provided any evidence that pelleted or unpelleted soybean meal differed nutritionally.
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