Lysine and Tryptophan Supplementation of Low-Protein, Corn-Soybean Meal Diets for Lactating Swine

Abstract

A total of 454 crossbred sows, gilts, and their litters were utilized to study the effects of lysine and(or) tryptophan supplementation of low-protein, corn-soybean meal diets fed during a 28-d lactation. Treatments were imposed on d 1 of lactation. In the first experiment, 168 sows and gilts were fed a 12% crude protein (CP), corn-soybean meal (CS) diet (12%), a 12% CP,CS + .18% L-lysine(.)HCl diet, (12% + L), or a 14% CP,CS diet (14%). Sows fed the 12% + L diet demonstrated a decreased (P .10) on sow milk composition or yield. Plasma levels of threonine (P < .0003), valine (P < .094) and urea (P < .006) were lower when sows were fed the 11 + L diet; tryptophan addition resulted in increased plasma methionine (P < .045), in comparison to those fed the 14% diet. When gilts were fed the 11% diet milk yield was increased (P < .009), total milk N decreased (P < .087), casein N increased (P < .016) and residual N decreased (P < .0007) in comparison to those fed the 14% diet. Milk yield and composition from gilts showed no response to tryptophan supplementation. Plasma levels of threonine (P < .07) and valine (P < .04) were decreased when lysine was supplemented. Plasma amino acids and urea did not respond to tryptophan supplementation. The results of these two studies suggest that lysine is limiting and tryptophan may be marginally limiting in the 11% CP,CS diet for the lactating sow, and that neither amino acid is limiting for the lactating gilt. Blood criteria suggest lysine is limiting for both the lactating sow and the gilt when fed the 11% CP,CS diet.