EFFECTS OF DIETARY SULFUR AMINO-ACIDS AND CRUDE PROTEIN ON THE PERFORMANCE OF FINISHING BROILERS

The effects of different combinations of dietary methionine+cystine (M et+Cys) and dietary crude protein (CP) in finishing broilers were inve stigated in two growth studies. In Exp. 1, male broilers 29 to 42 days of age were fed 18 diets containing 16.9%, 18.7%, or 20.4% CP with si x levels of Met+Cys within each protein level. Similarly, in Exp. 2 an other 12 diets containing either 18.0 or 21.5% CP were fed to male bro ilers 29 to 48 days of age. In general, the Met+Cys requirement for op timum feed conversion was higher than for maximum growth. In both expe riments, between 0.80% and 0.85% methionine+cystine optimized feed con version. These dietary levels were valid for a 13.05 MJ ME/kg diet fed to broilers growing from 1.2 kg to 2.2 kg (Exp. 1), or for a 13.60 MJ ME/kg diet fed to broilers growing from 1.3 kg to 3.0 kg (Exp. 2). Th e Met+Cys requirement was not consistently affected by the dietary CP content in Exp. 1. In Exp. 2, increasing dietary CP from 18.0% to 21.5 % tended to increase the Met+Cys requirement for optimum Feed conversi on. A dietary CP level of 18.0% to 18.7% supported performance and car cass fat deposition equal to diets containing 20.4% or 21.5% CP, respe ctively, when the sulfur amino acid content was adequate.