Forty eight commercial hybrids, barrows and females with 5.47 ± 0.21 kg, were allotted to a randomized block design with four treatments and six replications, to determine the best lysine level until 11.9 ± .35 kg and subsequent effects at 19.0 kg. The chemical composition of body fractions and the carcass and empty body accretion rates were determined. The studied digestible lysine levels in the nursery phase were 1.16 at 1.46%. No effects were observed on the chemical composition of the offal and blood, characterizing independence of lysine levels. The response to carcass and empty body accretion rates of protein and water was ascendant, as lysine levels increased, characterizing higher efficiency of utilization and direction of lysine for protein synthesis of the musculature. In the second phase, significant effects were observed, but the animals that were previously fed diet with smaller lysine levels tended to accumulate more protein and water in the carcass and empty body. Possibly, being in nutritional deficit, physiologically tolerate, the new diet provided the previous demand, but can not provide the demand for protein synthesis of the animals that were fed higher accretion rates of protein and synthesis ascent in the initial-1 phase. The positive responses for increasing lysine concentration in the diet of piglets from 5.5 to 11.9 kg suggest a need for new evaluations with lysine and metabolizable energy levels above the ones used, in order to establish the maximum efficiency of protein accretion rates. Studies in subsequent phases may add information of better nutritional levels for pig.
nursery; protein and lipid deposition; digestible lysine
