Determining the Optimal Tryptophan:Lysine Ratio for the Segregated Early-Weaned Pigs (25 to 50 LB)

Kansas State University Swine Research. A 21 d growth trial was conducted to evaluate the effects of increasing the apparent digestible tryptophan:lysine ratio on growth performance of the 25 to 50 lb pig raised in a high-health, segregated early-weaning (SEW) system. Ten diets were fed with two levels of lysine (.75% and 1.10% apparent digestible lysine) and five apparent digestible tryptophan levels (13, 16, 19, 22, or 25% of lysine). Feeding the high dietary lysine consistently improved ADG and F/G and reduced ADFI. Increasing the tryptophan: lysine ratio did not improve overall performance. Based upon our results, the dietary tryptophan level to maxi- mize growth performance in the 25 to 50 lb pig is not greater than 13% of apparent digestible lysine.