Fifty hybrid gilts, with high genetic potential for lean gain and initial and final average weight of 30.0 ± 0.45 and 59.9 ± 2.53 kg, respectively, were used in an experiment to evaluate diet with different levels of lysine. An experimental design of randomized blocks, with five treatments, five replicates and two animals per experimental unit, was used. The treatments corresponded to a basal diet with 17.5% crude protein, supplemented with five levels of HCl-L-lysine, resulting in diets with 0.80, 0.90, 1.00, 1.10, and 1.20% of total lysine. There were no effects of treatments on daily weight gain and serum urea concentration, however, daily feed intake and daily lysine intake increased linearly with the dietary lysine level. There was a quadratic effect of lysine levels on feed:gain ratio, that increased up to the total lysine level of 1.16% (0.347%/Mcal of DE) or 1.05% (0.315%/Mcal of DE) of digestible lysine, corresponding to the total and digestible lysine intake of 21.8 and 19.7 g/day, respectively. There was no effect of treatments on protein percentage, however, the water percentage in carcass linearly decreased. There was quadratic effect of treatments on fat percentage and fat deposition rate in carcass, that decreased up to the lysine level of 1.09 and 1.12%, respectively. The protein deposition rate improved quadraticly up to the level of lysine of 1.04%. It was concluded that gilts with high genetic potential for lean gain, from 30 to 60 kg require 1.16% of total lysine or 1.05% (0.315%/Mcal of DE) of true digestible lysine, corresponding to total and digestible lysine intake of 21.8 and 19.72 g/day, respectively, for maximal performance. The level of total lysine of 1.04% or 0,93% of digestible lysine proportioned the best protein deposition rate.
carcass; genotype; growing phase; lysine; requirement; urea
