The experiment was conducted to determine the effect of dietary methionine + cystine (met + cys) requirement of 1-to-21-day-old broiler chicks on thermoneutral environment. Four hundred Avian Farm male broiler chicks were assigned to a randomized experimental design with five treatments (0.756, 0.810, 0.866, 0.920, and 0.976% of met + cys), eight replicates of ten birds. Weight gain (WG), feed:gain ratio, met + cys intake, protein deposition of absolute weights of liver, gizzard, and lung and relative weights of lung were affected by the increasing dietary met + cys levels. No effect of met + cys levels on feed intake, fat deposition, absolute weights of carcass, proventriculus, heart, and intestine or relative weights of heart, liver, gizzard, proventriculus, lung and intestines was verified. The best WG was observed at 0.866% met + total cys (0.790% met + digestible cys calculated) level, corresponding to 69% met + cys/total lys ratio (72% for digestible) and the best feed:gain ratio value was observed at 0.894% met + total cys (0.822% digestible calculated) level, corresponding to 72% met + cys/ digestible lys total ratio (74% met + cys/digestible lys ratio), for broiler chicks on thermoneutral environment.
nutritional requirement; performance; sulphurous amino acids; thermal environment
