SUMMARY
This study was conducted to evaluate the effects of dietary methionine + cystine levels on performance, carcass characteristics and immune response of weanling pigs. It was used 360 piglets, 180 males and 180 females, weaned at 20.3 days of age and initial weight of 5.43 ± 1.17kg. Was used the experimental design of randomized blocks in a 5x2 factorial design, with five levels of total methionine + cystine (0.70; 0.77; 0.85; 0.93 e 1.01%) and two forms of immune system activation (vaccinated and unvaccinated), with four replications and nine animals per experimental unit. There was no interaction between the methionine + cystine levels and the degree of activation of the immune system of animals for all parameters evaluated. The immune system activation decreased by 7% feed intake and 5% in daily weight gain of the animals. Methionine and cystine levels linearly improved feed conversion and daily protein deposition on the carcass as the level of sulfur amino acids in the diets increased. Pigs from six to 16 kg, independent of immune system activation, require 0.90% of total methionine + cystine, which corresponds to a daily intake of methionine + cystine 4.44 g/day and a ratio of 58% methionine + cystine: lysine.
amino acids; ideal protein; immunity; protein deposition
