Two growth studies were conducted to determine the Met and Lys requirements of growing cattle. In each 84-d trial, steer calves were fed individually diets containing 44% sorghum silage, 44% corn cobs, and 12% supplement (DM basis) at an equal percentage of BW. In Trial 1, 95 crossbred steers (251 kg) were supplemented with urea or meat and bone meal (MBM). Incremental amounts of rumen-protected Met were added to MBM to provide 0, .45, .9, 1.35, 3, and 6 g/d metabolizable Met. In Trial 2, 60 steers (210 kg) were supplemented with urea or corn gluten meal (CGM). Incremental amounts of rumen-protected Lys were added to CGM to provide 0, 1, 2, 3, 4, 5, 6, 8, and 10 g/d metabolizable Lys. Supplementation with MBM and CGM increased the supply of metabolizable protein to the animal. Steers fed MBM plus 0 Met gained 49 g/d more than steers fed urea, whereas steers fed CGM plus 0 Lys gained 150 g/d more than steers fed urea. Supplementation of rumen-protected Met and Lys improved ADG in steers fed MBM and CGM, respectively (P < .10). Nonlinear analysis, comparing gain vs supplemental Met and Lys intake, predicted supplemental Met and Lys requirements of 2.9 and .9 g/d, respectively. This amount of additional Met promoted .13 kg/ d gain greater than MBM alone, and this amount of additional Lys promoted .10 kg/d gain greater than the CGM alone. Metabolizable Met and Lys requirements were predicted from Level 1 of NRC (1996) calculated metabolizable protein supply, amino acid analysis of abomasal contents, and the maximum response to supplemental AA. Steers gaining .39 kg/d required 11.6 g/ d Met or 3. 1% of the metabolizable protein requirement, whereas steers gaining .56 kg/d required 22.5 g/d Lys or 5.7% of the metabolizable protein requirement.
ABSTRACT:A finishing trial and a metabolism trial were conducted to determine the effect of supplemental metabolizable Lys level on finishing calf performance and to estimate the metabolizable Lys requirement of finishing calves. The finishing trial included 60 individually fed crossbred beef steer calves (237 kg; SD = 20 kg) supplemented with either incremental amounts of rumen-protected Lys and Met, or Met alone. Addition of Lys and Met improved gains and efficiencies (quadratic; P < .02) during the first 56 d. There was no response to supplemental Met alone, suggesting that supplemental Lys rather than Met was responsible for the improvement in performance. Using nonlinear analyses to compare gain relative to supplemental Lys intake, maximum gain was determined to be 2.10 kg/ d, or .27 kg/d above the zero Lys control, at a supplemen-
ABSTRACT:In situ, digestion, and growth studies were conducted to evaluate four meat and bone meals and six poultry by-product meals as sources of escape protein and to predict the first-limiting amino acid for growing calves. Escape protein values, determined by 12-h in situ incubation, ranged from 41.7 to 51.0% of CP for meat and bone meals; poultry by-product meals ranged from 32.0 to 39.8%. True protein digestion in the gastrointestinal tract of lambs differed among protein sources ( P < .05), ranging from 79 to 95%. In each of three growth trials, 60 steers (258 ± 24, 241 ± 23, and 230 ± 16 kg for Trials 1, 2, and 3, respectively) were supplemented with 4 of the 10 protein sources along with a urea supplement. Protein sources were fed at 30, 40, 50, and 60% of the supplemental CP, with urea supplying the remainder. Protein efficiency differed among treatments ( P < .10), ranging from .61 to 1.55. Amino acid composition was determined for each protein source, and the individual metabolizable amino acids were regressed on the protein efficiency values. Escape protein values were correlated ( R 2 = .75) with protein efficiency but had a negative slope. Metabolizable methionine was the only amino acid moderately correlated ( R 2 = .40, slope = 1.9) to protein efficiency, whereas other amino acids either correlated poorly or had negative slopes. These data indicate that the protein value of meat and bone meal and poultry by-product meal is limited by the amount of metabolizable methionine they contain.
Two receiving and two finishing trials evaluated energy source and escape protein supplementation for calves. In receiving Trial 1, 398 calves (257 ± 24 kg BW) were used in a 2 × 2 factorial arrangement of treatments. Energy sources were dryrolled corn (DRC) and wet corn gluten feed (WCGF); each was fed without or with supplemental escape protein (EP). Calves fed WCGF gained slower ( P < .05) and consumed less DM ( P < .01) than calves fed DRC. Feed efficiency improved ( P < .10) with EP supplementation. In finishing Trial 1, 240 calves (305 ± 21 kg BW) were used. The arrangement of treatments was the same as in receiving Trial 1. Calves fed DRC/WCGF tended ( P = .15) to be more efficient and consumed less DM ( P < .05) than calves fed DRC. In receiving Trial 2, 315 calves (252 ± 23 kg BW) were fed diets similar to those fed in receiving Trial 1. Calves fed WCGF consumed less DM ( P < .01), gained similarly ( P > .15), and were more efficient ( P < .10) than calves fed DRC. In finishing Trial 2, 320 calves (298 ± 23 kg BW) were fed diets containing DRC, DRC/WCGF, high-moisture corn (HMC), HMC/WCGF, and DRC/HMC; each was fed without or with supplemental EP. An energy source × protein supplement interaction was detected for gain ( P < .05) and efficiency ( P < .01). Results suggest that WCGF has a NE g greater than DRC in receiving diets and a NE g similar to that of DRC but lower than that of HMC in finishing diets.
We evaluated feather meal (FTH) and poultry by-product meal (PBM) as complementary protein sources for growing calves. In a replicated 84-d growth trial, individually fed steer calves (n = 120; 252 +/- 24 kg) were supplemented with urea or with graded levels of soybean meal (SBM), FTH, PBM, or 2/3 FTH:1/3 PBM (CP basis). Protein efficiency, calculated as gain above the urea control vs natural protein intake using the slope-ratio technique, was greater for FTH than for SBM, PBM, and 2/3 FTH:1/3 PBM (P < .10). Addition of ruminally protected methionine and lysine did not affect protein efficiency (P > .30) for FTH, PBM, or 2/3 FTH:1/3 PBM. Even though true protein digestibility in the gastrointestinal tract in a trial with lambs was similar (P > .15) for FTH (83.1%) and PBM (91.2%), escape protein was greater for FTH (66.8%) than for PBM (43.6%). Analyses were conducted to estimate intestinal flow of amino acids relative to requirements for live animal gain, and no obvious amino acid deficiencies were present. The lack of a response in protein efficiency to ruminally protected methionine and lysine suggests that FTH and PBM are adequate in these amino acids. Although FTH and PBM are excellent sources of metabolizable protein, there was no complementary response in protein efficiency between them.
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