Determining high-lysine sorghum amino acid digestibility and the effects on nursery pig performance

Two experiments determined the SID of AA in a high-lysine sorghum cultivar, followed by a growth trial to determine its effects on pig performance using increasing feed-grade AA at the expense of soybean meal. In Exp. 1, ten barrows (initially 25.9 kg) were surgically fitted with a T-cannula at the terminal ileum and randomly assigned to 1 of 5 diets in a 5-period, cross-over design. Experimental diets included a corn-based diet, a diet containing highlysine sorghum, or two diets with either white or red sorghum cultivars. The fifth experimental diet was N-free to determine endogenous AA loss. In corn, SID CP, lysine, methionine, threonine, and valine were greater (P < 0.020) than sorghum-based diets, with no evidence for differences among the sorghum cultivars. In Exp. 2, a total of 293 pigs (initially 9.6 kg) were used. Dietary treatments were randomly assigned 20 d after weaning and consisted of a cornbased diet, a diet based on conventional sorghum, and 4 diets with high-lysine sorghum with 10 replications/ treatment. The corn-based, conventional sorghum, and the first high-lysine sorghum (low) diets each contained the same amount of soybean meal with varying amounts of feed-grade AA. The 3 remaining high-lysine sorghum diets included incrementally increasing amounts of feed-grade AA (lowmedium, medium-high, and high), replacing soybean meal. Overall, there was no evidence for differences in ADG or ADFI between treatments. However, pigs fed the high-lysine sorghum with the greatest amount of feed-grade AA had decreased G:F (P = 0.045) compared with those fed other experimental diets. In summary, SID AA values for the high-lysine sorghum in this study were not different from sorghum cultivars; however, these values were all lower when compared with corn. When nursery diets were formulated on an equal SID AA basis, there were no differences in ADG among pigs fed any of the diets.