Effect of protein level on performance, nitrogen utilisation and carcass composition in finisher pigs

For 6 weeks, 256 female finisher pigs (initially 53.9 kg) were fed four dietary treatments of 136, 148, 159 and 168 g crude protein (CP)/kg diet. The latter diet was the 159 g CP/kg diet supplemented with dispensable amino acids, to study the effect of excess CP. Week 4 included use of metabolic cages. Feed intake, gain and feed utilisation were not significantly affected. Plasma urea (P < 0.001) and urinary nitrogen (P = 0.01) decreased linearly by lowering CP. The weight of the carcass tended to increase linearly by reducing CP, but neither nitrogen retention nor carcass meat percentage and back fat depth differed among treatments. In conclusion, the study indicated that CP could be decreased to 136 g/kg as-fed for growing pigs in the weight range 50–100 kg without negative impact on growth performance and carcass traits. Moreover, leanness was not affected by excess CP