Amino acid composition of growing pigs is affected by protein and energy intake.

Ninety-five female pigs from 20 to 45 kg body weight were used to elucidate the effects of energy and protein intake on the amino acid composition of the protein in the carcass, organs and empty body of growing pigs. In a 2 x 15 factorial arrangement, protein intake ranged from 127 to 350 g/d in 15 graduated steps; and the digestible energy allowances were 15.8 and 18.8 MJ/d. Whole-body amino acid contents (g/16 g nitrogen) were (means +/- SEM) lysine 6.64 +/- 0.028, methionine 2.11 +/- 0.012; threonine 3.62 +/- 0.016 and total essential amino acids 42.8 +/- 0.16. The organ fraction contained 14.8 and 15.8% (SEM 0.13) of whole-body protein at the low and high energy levels, respectively. The concentrations of essential amino acids were 41.8 +/- 0.19 and 48.4 +/- 0.13 g/16 g nitrogen in the carcass and organs, respectively. Concentrations of a number of amino acids (in carcass, organ and whole-body protein and in protein deposited between 20 and 45 kg, were affected by protein and/or energy intake. The amino acid pattern of the newly deposited protein was slightly different from that of the empty body protein. The changes in amino acid contents were presumably the result of effects of protein and energy intake on the proportions of muscle and non-muscle carcass tissues and on relative weights of blood and viscera. Consequences of these changes for the amino acid requirements are discussed.