Sixty crossbred piglets, with average initial weight of 15.1 ± 0.50 kg and 56 ± 3.6 days old were used to evaluate the dietary crude protein levels, for barrows in the initial growing phase, under low temperature environment (15ºC). The animals were allotted to a randomized blocks design, with five treatments, six replications and two animals per experimental unit. The treatments consisted of diets with 17.0, 18.0, 19.0, 20.0, and 21.0% crude protein (CP). The dietary crude protein levels affected daily weight gain, that increased in a quadratic way up to 19.6%. Feed:gain ratio also changed in a quadratic way, increasing up to 20.0%. Daily feed and digestible energy intakes were not influenced by the treatments. The best fit was obtained with the LRP discontinuous model, which estimated the crude protein level at 20%, when the data reached a plateau. The treatments influenced the protein deposition rate, that increased linearly, while the fat deposition rate did not change. It was concluded that the dietary crude protein level of 20.0%, associated to a daily intake of 10.7g total lysine, showed the best results of performance for barrows from 15 to 30 kg, under low temperature environment.
males barrows; cold; performance; piglets; protein levels
