Escape protein for beef cows. I. Source and level in corn plant diets
1991
Rock, D.W. | Ward, J.K. | Klopfenstein, T.J.
Two gestating cow winter grazing trials and two lactating cow drylot trials were conducted to evaluate the use of a slowly degraded protein source in corn plant diets for mature beef cows. Gestating beef cows grazing cornstalks were supplemented with .86 kg/(cow.d) of a 20% crude protein equivalent (CPE) pellet (DM basis). In Trial 1 cows fed diets containing 80% dehydrated alfalfa meal (high DEHY) gained more weight (P < .05) than those fed diets containing 40% dehydrated alfalfa meal (low DEHY) or urea but not more than the cows fed soybean meal (SBM); however, no differences among treatments were observed in Trial 2. Four lactation diets composed of ground corncobs and corn silage were supplemented with either urea, SBM, or two levels of dehydrated alfalfa meal (DEHY) as N sources. The same amount of supplemental N was fed in both trials, consisting of .31 kg of natural protein for the SBM and low DEHY treatments or .42 kg for high DEHY. Ammoniated corncobs replaced 35% of the ground corncobs in Trial 4. Diets were calculated to contain (DM basis) 55% TDN and 9% CPE in Trial 3 and 11% CPE in Trial 4. In Trial 3, lactating cows supplemented with DEHY gained more weight (P < .10) than those fed the urea supplement but not more than those fed SBM. Gains by cows fed the urea- and SBM-supplemented diets were not different (P > .10). Cow weight gains in Trial 4 were not affected by type of protein supplementation. The cows supplemented with high DEHY in Trials 3 and 4 produced the most milk (P < .05) when measured by weighsuckle-weigh but not when measured by hand milking. No differences were observed in calf performance and milk composition.
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