The Influence of Methionine Supplementation of 12, 14 and 16 Percent Protein Corn-Soybean Oil Meal Diets upon Nitrogen Balance of Growing Swine

Abstract

The nitrogen balances of growing pigs fed an 11.8% crude protein corn-soybean oil meal diet containing 0.10 to 0.12 and 0.58% of tryptophan and lysine, respectively, were not improved by supplementation of the diet with 0, 0.025, 0.05 and 0.10% of DL-methionine to provide final methionine levels of 0.22, 0.245, 0.27 and 0.32% of the diet. It was suggested that lysine may have been inadequate to the extent that it limited the response of growing pigs to methionine supplementation in the presence of supplemental tryptophan. This lower protein diet also contained less than 0.7% of isoleucine which could have limited nitrogen retention if the requirement for isoleucine is not a function of protein content of the diet. Although nitrogen retention values for pigs fed a 15.8% crude protein diet supplemented with several levels of DL-methionine and DL-tryptophan were greater, on the average, than those values obtained for pigs fed a 13.8% crude protein diet supplemented in an identical manner, there was some overlapping of mean nitrogen retention values for the various treatments on the two levels of dietary protein. The addition of 0, 0.025, 0.05 or 0.1% of supplemental DL-methionine to a 13.8% protein diet with or without 0.04% of supplemental DL-tryptophan did not result in significant differences in nitrogen balances of growing swine. The levels of 0.126, 0.25 to 0.27 and 0.69% tryptophan, methionine and lysine, contained in the 13.8% protein diet, when 0 or 0.025% of supplemental DL-methionine was added, appeared to be adequate to promote satisfactory nitrogen retention by growing pigs fed the diet at approximately 4.00% of their body weights. The 15.8% protein diet used in these investigations appeared to supply dietary nitrogen in excess of the needs of growing pigs, particularly heavier weight pigs, as evidenced by a marked tendency toward increased loss of nitrogen by urinary excretion.