Determination of the fourth-limiting amino acid in swine diets containing nutridense® corn

Two studies were conducted to determine the fourth-limiting amino acid in swine diets containing NutriDense® corn. Both experiments were conducted at a commercial swine research facility in southwest Minnesota. In Exp. 1, 1,259 pigs (initially 82.1 lb, PIC) were used in a 28-d study. Pigs were blocked by weight, and were randomly allotted to one of six dietary treatments. Pigs were fed NutriDense® corn-soybean meal-based diets. The treatments were 1) a positive control diet containing 0.15% L-lysine HCl and 0.015% added L-threonine; 2) a negative control diet with 0.45% L-lysine HCl, 0.085% added DL-methionine, and 0.15% added L-threonine; 3) treatment 2 with 0.05% L-isoleucine; 4) treatment 2 with 0.05% L-valine; 5) treatment 2 with 0.05% L-tryptophan; and 6) treatment 2 with a combination of 0.05% L-isoleucine, 0.05% L-tryptophan, and 0.05% L-valine. Pigs fed the positive control and the diet with the combination of added isoleucine, tryptophan, and valine had greater ADG (P<0.05) than all other treatments. Also, pigs fed added isoleucine or tryptophan had greater ADG (P<0.05) than pigs fed the negative control with those fed added valine being intermediate. Pigs fed the diet with the combination of added isoleucine, tryptophan, and valine had greater ADFI (P<0.05) then pigs fed the negative control. There were no significant differences in F/G. In Exp. 2, 1,038 pigs (initially 170.4 lb, PIC) were used in the 28-d study with six dietary treatments similar to Exp. 1 to determine the fourth-limiting amino acid in late finishing pigs. Overall, pigs fed the positive control diet had greater (P<0.05) ADG and lower (P<0.05) F/G then pigs fed the negative control diet and those fed either L-isoleucine, L-tryptophan, or L-valine. Pigs fed the diet containing added tryptophan or the combination of isoleucine, tryptophan, and valine had improved (P<0.05) ADG and F/G compared with those fed the negative control, or added isoleucine or valine. Pigs fed added isoleucine and valine had greater (P<0.05) ADG than pigs fed the negative control diet. There was no difference amongst the treatments for ADFI. These results suggest that in the 80 to 130 lb growing pig, tryptophan and isoleucine are the co-limiting fourth amino acid in diets containing NutriDense® corn. In 170 to 220 lb pigs, tryptophan appears to be fourth-limiting followed by isoleucine and valine.