Seventy and six lactating crossbred sows of medium genetic potential with initial weight of 207.0 ± 32.0 kg and reproductive cycles order of 3.53 ± 2.11 were used to evaluate digestible threonine levels in the lactation phase. The animals were allotted to a randomized blocks experimental design with four treatments (0.589, 0.627, 0.665, and 0.703% of digestible threonine) and nineteen replications, in which each experimental unit was onsisted by a female. There was no effect of digestible threonine levels on the weight of sows at weaning time, fat thickness (FT) and corporal protein composition at weaning time. The loss of weight of the sows during the lactation reduced in a linear form with the increase of the digestible threonine level. There was no effect of digestible threonine levels on FT variation during the lactation, however affected the corporal protein mobilization that linearly reduced with the increase of the digestible threonine level. There was no effect of digestible threonine levels on feed intake, lysine and digestible energy, however, was observed linear increase of the intake of digestible threonine with its increase level in the diet. The digestible threonine levels did not influence the energy efficiency of the sows; weaning - estrus interval and the performance of the pigs and litters. Lactating sows of medium genetic potential require 0.589% of digestible threonine, corresponding to daily consumption of 28.5 g and a digestible threonine: digestible lysine ratio of 62%.
amino acids relation; fat mobilization; ideal protein; milk production; protein mobilization
