Combinations of rendered protein meals for growing calves

Complementary responses between rendered protein meals were investigated in this study. In a preliminary trial using 12 mature wethers in two replications, there was no difference (P greater than .20) in N digestibility between meat and bone meal (MBM; 96.7%), feather meal (FTH; 89.8%), and soybean meal (SBM; 98.7%). In a 112-d growth trial, individually fed calves (n = 120; 230 kg) received graded levels of FTH, MBM, 50:50 MBM-FTH (CP basis), or SBM with or without tryptophan (Trp) supplementation. Additions of Trp increased plasma Trp levels (P less than .05) but failed to improve efficiency of protein utilization (P greater than .35). Pooled results showed that this efficiency was greater (P less than .05) for FTH (1.47) than for MBM (1.04), FTH:MBM (.80), or SBM (.66). A trial was conducted to determine whether Trp addition reduces growth response to FTH:MBM (50:50) combinations. Calves (n = 230; 285 kg) were blocked by sex and weight into six replications and received FTH:MBM supplying 35% of the supplemental CP fed alone or with a high or low level of Trp supplement. Negative (urea only) and positive controls were included. Calves receiving FTH:MBM combinations gained faster (P less than .10) and were more efficient (P less than .10) than urea-supplemented calves. Performance was not altered by Trp addition. Calves (n = 120; 230 kg) were individually fed in two replications (43 or 48% CP MBM in Replications 1 and 2, respectively) of a growth trial to determine whether there was a complementary response between blood meal (BM) and MBM.(ABSTRACT TRUNCATED AT 250 WORDS)