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The amino acid composition of body protein is considered constant, although there is evidence that the amino acid pattern in pigs may be altered by different factors. Pigs with different body composition and protein deposition rates, like fatty and lean pigs, may differ in amino acid composition, with possible consequences on their amino acid requirements. The objective of this study was to investigate the effects of genotype and dietary lysine deficiency on amino acid composition of carcass and muscles of Iberian and Landrace × Large White pigs. Twenty-eight barrows (10 kg body weight), 14 from each breed, were used. Animals were randomly assigned to two experimental diets according to a factorial arrangement (two breeds × two diets). Diets were isonitrogenous and isoenergetic (200 ± 1 g CP/kg dry matter; 14.7 ± 0.1 MJ ME/kg dry matter) and with identical chemical composition except for lysine concentration (10.9 and 5.20 g lysine/kg dry matter, for lysine-adequate diet and lysine-deficient diet respectively). Pigs were individually housed, and daily feed allowance was adjusted on a weekly basis according to body weight. Pigs were slaughtered at 25 kg body weight.
Isoleucine, valine and phenylalanine concentration were higher in carcass protein of Iberian pigs. In longissimus muscle, higher concentration of arginine, isoleucine, phenylalanine, lysine and valine, and lower of methionine were detected in Iberian pigs, whereas phenylalanine, leucine, lysine, threonine and methionine concentration decreased, and arginine increased when pigs were fed lysine-deficient diet. Genotype and lysine deficiency effects were moderate in the amino acid composition of protein of biceps femoris muscle.
The results show that amino acid proportions in protein of carcass and longissimus muscle can be influenced by pig genotype and conditions of lysine shortage. The biceps femoris muscle, with different functional and metabolic properties, shows more constant amino acid composition than longissimus, which seem to prevail independent from genotype or nutritional challenges. Both fatty and lean pigs responded in general terms in a similar way to a dietary lysine deficiency, modifying the rate of body and muscle growth and modulating the protein composition of specific carcass components, a fact possibly related with their different body functions.
Palma‐Granados P, Lara L, Seiquer I, Aguilera JF, Nieto R. Genotype and dietary lysine deficiency affect carcass and muscle amino acid composition of pigs growing from 10 to 25 kg body weight. Journal of Animal Physiology and Animal Nutrition. 2019; 103(6): 1857-1865. https://doi.org/10.1111/jpn.13176