INFLUENCE OF PROTEIN-CONCENTRATION ON THE RESPONSE OF BROILERS TO SUPPLEMENTAL DL-METHIONINE

This experiment was conducted with male broiler chickens from 15 to 35 days of age to determine the effect of dietary protein content on the requirement for sulphur-amino acids. Six levels of DL-methionine were added to diets containing 20.5 or 24.2% crude protein. At each protei n concentration there was a response in growth rate, feed efficiency, and carcass quality to methionine supplementation. Plateauing in growt h rate or feed efficiency was not achieved with the highest methionine supplementation. Thus the requirement for maximum growth and optimum feed efficiency was more than 0.86% Met + Cvs with 20.5% CP or more th an 0.95% Met + Cys with 24.2 CP. The sulphur amino acid requirement in creased almost in direct proportion to the dietary protein level (with a ratio of about 0.025% additional Met + Cys per %-point additional p rotein). It is suggested to consider this relationship in diet formula tion. Carcass quality was significantly improved by increasing protein and sulphur-amino acid concentrations. Slaughter yield and breast mea t yield seemed to be more influenced by methionine level than by prote in content, while fat content responded to both protein and methionine .