Growth and nitrogen balance studies with growing pigs fed on diets containing normal oropaque-2 maize, meat and hone meal, and synthetic amino acids

摘要

Two experiments were conducted with pigs of 23-50 kg body weight to examine: (1) the growth (Experiment 1) and nitrogen retention (Experiment 2) supported by diets based on either normal maize oropaque-2maize, each containing meat and bone meal as the only source of supplementary protein; and (2) the orders in which essential amino acids are limiting in these diets. Sixteen diets were formulated in a 24 factorial arrangement, the factors being maize type and added lysine, tryptophan, and methionine. Diets contained comparatively low concentrations of crude protein and high concentrations of nicotinic acid. Diets based onopaque-2maize promoted much faster and more efficient growth than those containing normal maize, which primarily reflected the higher tryptophan content of the mutant. From the significant main effects and interactions on rate of gain, feed conversion ratio, and nitrogen retention, it was concluded that tryptophan and lysine were the first- and second-limiting amino acids respectively in both the normal maize andopaque-2maize diets. Methionine may have been marginally third-limiting in theopaque-2maize diet, but it did not seem to be limiting in the normal maize diet, although it was one of the more limiting amino acids.