Limiting amino acids in sorghum and threonine requirement of sorghum-soybean meal diets for growing and finishing swine

Abstract

Limiting Amino Acids In each of the two feeding experiments, 64 crossbred pigs were individually fed ad libitum, fortified sorghum diets supplemented with threonine, methionine and tryptophan individually and with all combinations to determine the second and third limiting amino acids in sorghum for growing and finishing pigs (17.8 and 55.1 kg average initial weight, respectively). Four barrows and four gilts were fed one of the following isonitrogenous diets: basal composed of sorghum + L-lysine, vitamins, minerals and antibiotics (B); B + L-threonine (T); B + DL-methionine (M); B + DL-tryptophan (W); B + T + M; B + T + W; B + M + W and B + T + M + W. All amino acids were added to provide 120% of the calculated requirements for a 9.5% protein diet, based on the National Research Council (N.R.C.) recommendations for 16% protein grower and 14% finisher diets. In the growing pig trial, diets supplemented with threonine supported higher (P<.001) average daily gain (ADG, g) and gain/feed (G/F, g/kg) than those without supplemental threonine (396 vs 279 and 298 vs 232, respectively). In contrast, ADG and G/F were only slightly improved (P>.10) when diets with methionine or tryptophan were compared to those without these amino acids (342 vs 333 and 272 vs 259 for methionine, 347 vs 328 and 267 vs 264 for tryptophan). These results clearly indicate that threonine is the second limiting amino acid in sorghum for growing swine. ...