A trial was carried out to determine lysine requirements for castrated males during finishing phase of two genetic swine groups, based on the ideal protein concept. Sixteen animals from genetic common group (GCG) were used and another sixteen, from the genetic improved group (GIG) were allotted to four treatments. The treatment consisted on a basal diets, based on corn and soybean meal containing 0.60% of lysine and other three diet, adding increasing lysine levels to achieve 0.75, 0.90 and 1.05% of total lysine. Synthetic amino acids were added (L-lysine HCl, DL-methionine, L-threonine and L-tryptophan) to keep amino acid levels according to the ideal protein profile. The plasma urea nitrogen (PUN) concentrations were recorded. The carcass traits were done with in vivo pigs using the Sono Grader ultra sound equipment. At the end of the experimental period, 12 animals were slaughtered and their carcasses were evaluated according to the Brazilian Method of Carcass Classification. It was observed no effect of lysine levels (LL) on PUN for different genetic groups. Lysine requirement for GIG pigs, during finishing phase (53 to 92 kg of live weight), is over 1.05%, whereas for GCG (50 to 90 kg of live weight) is 0.60% of total lysine.
amino acid; carcass traits; finishing swine; ideal protein; lysine; plasma urea nitrogen
