This study was conducted in order to determine the best relations of threonine with lysine for pigs from 28 to 49 days of age. For this 120 commercial crossbred pigs with high genetic potential for lean meat in the carcase, weaned at 28 days of age with an average initial weight of 7.45kg were used. The animals were allotted to a randomized block design, with five treatments (ratios of threonine and lysine) and controlling the initial weight, with eight replications and three animals per experimental unit. The treatments were the following digestible threonine and lysine: 0.50; 0.57; 0.64; 0.71; 0.78. - From 28 to 42 days and Period II - 28 to 49 days of Period I: piglet performance and values of haptoglobin and faecal score by periods were evaluated. The relations of threonine and lysine did not affect average daily feed intake and average daily weight gain of the animals. Quadratic effect of treatments on the feed conversion in periods I and II. There was no effect of treatments on haptoglobin levels and fecal score in the fifth and tenth day of the trial period. Best digestible threonine to lysine found for feed conversion were 0, 629 and 0 648, respectively for the I (28 to 42 days old) and II (28 to 49 days of age) periods.
industrial amino acid; performance; ideal protein