Abstract
Twenty-five mature Landrace x Yorkshire sows were used in an experiment to evaluate the tryptophan requirement of the sow during the first 3 weeks of lactation. A basal diet consisting of corn, starch and dextrose with added vitamins, minerals and essential amino acids was formulated to satisfy the currently recognized sow requirements for all essential nutrients except tryptophan. L-tryptophan was added to this diet to produce five diets containing: 0.046, 0.066, 0.091, 0.121 and 0.161% tryptophan, respectively. The sow's tryptophan requirement was estimated on the basis of nitrogen retention, milk production and composition, pig weight gain, and plasma essential amino acids and urea. Nitrogen retention, milk production and milk protein increased quadratically (P<.05) with increasing levels of tryptophan, generally reaching a plateau by 0.091% tryptophan. Pig gain increased linearly (P<.01) with tryptophan level. Changes in sow weight and backfat thickness were variable, and no significant treatment effects were observed. Plasma tryptophan increased in a sigmoid manner (cubic effect P<.001) as dietary tryptophan increased, with an inflection point at about 0.091% tryptophan. Copyright © 1974. American Society of Animal Science. Copyright 1974 by American Society of Animal Science.