Metabolizable protein for finishing calves

Five finishing cattle trials, four with calves and one with yearlings, were conducted to evaluate sources of supplemental CP in high grain diets. One metabolism trial was conducted to measure ruminal protein degradation and rate of passage of dry rolled corn (DRC), dry rolled grain sorghum (DRGS), corn silage, blood meal (BM), feather meal (FTH), and soybean meal (SBM). In finishing Trial 1, calves supplemented with BM/FTH/urea gained more efficiently during the first 41 d than calves supplemented with urea. Over the entire trial (199 d) gain and gain/feed were not affected by source of CP. Calves fed DRC gained more efficiently than calves fed DRGS. In finishing Trial 2, calves supplemented with SBM gained faster and more efficiently than calves supplemented with urea, FTH/urea or FTH/BM/urea during the first 28 d. Over the entire trial (187 d) gain and gain/feed were not affected by source of CP. During the first 28 d, gain and gain/feed were highly correlated to essential amino acid intake. In finishing Trial 3, calves had similar gains and efficiencies when supplemented with SBM or BM/urea at any period. In finishing Trial 4, calves which grazed cornstalks 74 d before finishing exhibited compensatory growth, as they consumed more feed, gained faster, but were less efficient in the feedlot than calves finished after weaning. Response (gain and gain/feed) to additional metabolizable protein was greater for compensating calves than noncompensating calves. In finishing Trial 5, yearlings supplemented with SBM/urea gained faster and more efficiently during the first 31 d than yearlings supplemented with FTH/urea, FTH/meat and bone meal/urea, or urea alone. Over the entire trial (117 d) source of supplemental CP had no effect on gain or gain/feed. In the metabolism trial, source of supplemental CP had minimal effects on ruminal parameters. Estimates of ruminal escape N for SBM, BM, FTH, DRC, DRGS, and corn silage were 52.3, 93.3, 91.7, 65.7, 63.6 and 23.3%, respectively