Fifty barrows (30.10 ± 0.48 kg to 60.08 ± 0.49 kg live weight were assigned to a completely randomized blocks design, with five digestible methionine plus cystine levels (0.448, 0.490, 0.531, 0.573, and 0.615%), five replicates and two animals per experimental unit, to evaluate the requirement of digestible methionine plus cystine The digestible methionine and cystine levels of the diet influenced the average daily gain that increased in a linear way. However, the linear response plateau model was what best adjusted the data that stabilized in a plateau starting from the level of 0.527% of digestible methionine plus cystine. The feed:gain ratio decreased in a quadratic way with the treatments, until the estimated level of 0.551%. It was not observed the effect of the treatments on the feed intake. The digestible methionine plus cystine intake increased linearly with the increase digestible methionine plus cystine levels in the diet. Effect of the treatments was verified on the protein deposition that increased quadraticaly until the level of 0.551%, while no effect was observed on fat deposition. It was concluded that digestible methionine plus cystine requirements for barrows maintained in high environmental temperature from 30 until the 60 kg are 0.527 and 0.551% of diet, correspondent to digestible methionine plus cystine:digestible lysine ratio of 63.5 and 66%, respectively, to highest weight gain and better feed:gain ratio and highest protein deposition in the carcass.
carcass; growing; heat stress; sulphurous amino acids
