Responses of pigs of different genotypes to a variation in the dietary indispensable amino acid content in terms of their growth and carcass and meat quality traits

We studied the response of pigs from two crossbred genetic lines (GL) in the 60 to 145 kg body weight interval to a variation in the indispensable amino acid (AA) content of their feed. Ninety-six barrows of two paternal GLs (Hypor Maxter and PIC 337) were housed in eight pens and fed quasi ad libitum on feeds differing in their standardized ileal digestible (SID) indispensable AA contents. Pigs in four pens received feeds containing 9.4 to 8.0 g/kg of SID Lys (HAA), considered non-limiting, while the others received feeds containing 8.5 to 6.5 g/kg of SID Lys (LAA). The two feeds had identical indispensable lysine, methionine, tryptophan and threonine contents per unit of crude protein (CP). Feed intake, growth, carcass weight, and the weights of the lean and fat cuts were recorded, and samples of longissimus lumborum were analyzed. Data were analyzed using a two-way factorial mixed model. The LAA feed lowered the estimated N excretion (p < 0.001) compared with HAA, without affecting growth, carcass or meat quality traits. Genetic line had trivial effects and the AA level × genotype interaction was never significant. The two pig genotypes did not differ sufficiently in growth potential and leanness to respond differently.