COMPLEMENTARY RESPONSES BETWEEN FEATHER MEAL AND POULTRY BY-PRODUCT MEAL WITH OR WITHOUT RUMINALLY PROTECTED METHIONINE AND LYSINE IN GROWING CALVES

We evaluated feather meal (FTH) and poultry by-product meal (PBM) as c omplementary protein sources for growing calves. In a replicated 84-d growth trial, individually fed steer calves (n = 120; 252 +/- 24 kg) w ere supplemented with urea or with graded levels of soybean meal (SBM) , FTH, PBM, or 2/3 FTH:1/3 PBM (CP basis). Protein efficiency, calcula ted 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 gastrointe stinal 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 a mino acids relative to requirements for live animal gain, and no obvio us amino acid deficiencies were present. The lack of a response in pro tein efficiency to ruminally protected methionine and lysine suggests that FTH and PBM are adequate in these amino acids. Although FTH and P BM are excellent sources of metabolizable protein, there was no comple mentary response in protein efficiency between them.