Digestible methionine plus cystine requirement for barrows maintained in thermoneutral environment from 30 to 60 kg

Fifty barrows from 29.97 +/- 0.36 kg to 60.38 +/- 0.49 kg were used to evaluate the requirement of digestible methionine + cystine. A completely randomized blocks design, with five digestible methionine + cystine levels (0.448; 0.490; 0.531; 0.573 and 0.614%), with five replicates and two animals per experimental unity, was used. The digestible methionine + cystine levels of the diet influenced in a quadratic way the average daily gain and the feed:gain being the level of digestible methionine + cystine estimated in 0.549% for the maximum weight gain and better feed:gain. No effect of the treatments on the feed intake was observed. The digestible methionine + cystine intake increased linearly as the digestible methionine + cystine levels in the diet increased. Quadratic effect of the treatments was verified on the fat and protein depositions in the carcass that increased until the levels of digestible methionine + cystine estimated in 0.548 and 0.547%, respectively. It was concluded that digestible methionine + cystine requirements for barrows maintained in thermoneutral environment from 30 to 60 kg is 0.549%, correspondent to digestible methionine + cystine:digestible lysine ratio of 66%.