Limiting Amino Acids in Low-protein Corn-soybean Meal Diets for Growing-finishing Swine 1 ,2

Experiments were conducted with growing and finishing swine to evaluate the effectiveness of various amino acid additions to low-protein corn-soybean meal diets. Two feeding experiments were conducted with growing swine each including a 16% protein positive control diet. In the first, a 14% protein diet served as the negative control while in the second trial it was a 12% protein diet. Amino acids were supplemented to the negative control diets in each experiment. Rate and efficiency of gains from feeding either 12 or 14% protein diets were inferior to those of pigs fed the 16% protein diet. Lysine additions to the 14% protein diet resulted in pig performance similar to those fed the positive control diet. The addition of both lysine and tryptophan to a 12% protein diet for growing swine equaled the performance of pigs fed the 16% protein diet. The firstand second-limiting amino acids for growing swine from the 12% diet was suggested as being lysine and tryptophan, respectively. A nitrogen balance trial supported the observations of these latter findings. The addition of methionine or threonine to amino acid supplemented diets resulted in reduced performance. Two group-feeding experiments with finishing swine initially weighing approximately 52 kg were conducted with a positive 13%and a