It was evaluated four crude protein (CP) levels in diets considered as commercial fed to barrows in the growing and finishing phases. A total of 48 barrows, from the same genetic strain, averaging initial weights of 30.8 ± 0.12 kg (growing phase) and 61.2 ± -0.89 kg (finishing phase), segregated in the production system, was used. The animals were allotted to randomized blocks design, composed of four treatment (level of CP) and six replications and two animals per experimental unit. The CP levels tested were: 19.5, 18.0, 16.5, and 15.0% in growing and 18.0, 16.5, 15.0 and 13.5% in finishing phases. There was no difference in the growing phase of barrows performance. Independently of the dietary CP levels, the nutritional requirements were supplied, in spite of the diet with 16.5% CP indicated greater economic viability, calculated as gross margin due to the feed. Similar to the growing phase, there were no differences among CP levels on performance and carcass characteristics of finishing barrows at slaughter. The gross margin due to the feed indicated that 15.0% CP in the diet offered greater economic gain for barrows from 60 to 100 kg. The results indicate that dietary protein changes, with main principal amino acids supplied not impaired the barrows performance. The creation and segregation conditions of commercial farm system in growing and finishing phases need considerations. Small variations between amino acids did not affect performance of barrows in the growing and finishing phases if the requirements of digestible lysine and others amino acids are maintained close to the indicated minimal relation.
carcass; digestible lysine; protein level; segregate breed
