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Availability of Trypotophan in Some Feedstuffs for Swin^{1 ,2,}

University of Nebraska, Lincoln 68583

Abstract

Two experiments were conducted to determine the availability of tryptophan (Try) from corn (NC), opaque-2 corn (OC), milo (M) and freeze dried alfalfa (FDA) when fed to swine. The first experiment consisted of a growth trial involving 96 baby pigs and eight treatments. The basal diet containing .06% Try and 24.5% protein was supplemented with .015%, .030% and .045% L-Try. These four diets were used to establish a standard curve for growth. The other treatments were formed by adding the feedstuffs as the source of Try to the basal diet. Availabilities were determined by comparing growth responses. Try availabilities from NC, OC, M and FDA were 70, 58.3, 70 and 83.3%, respectively, when gain was used as the response criterion, and 77, 65, 85 and 80% when gain/feed was the response criterion.

Plasma Try, muscle RNA and DNA and muscle polysome profiles were used as criteria for assessing the availability of Try. Dietary levels of Try showed a quadratic effect (P<.01) on plasma Try and no apparent effect on the muscle parameters.

In the second experiment, post-prandial changes in blood Try levels were used as a measure of Try availability from FDA. Analysis of blood from pigs fed the dietary treatments (growth curve) used in experiment 1 plus the treatment with FDA as the source of Try showed an increase in Try level that peaked irregularly between 15 and 45 min post-feeding followed by a marked decrease that plateaued at about 2 to 2.5 hours. The net decrease in plasma Try as well as the rate of the decrease (slope between the peak maximum and the plateau) appeared to be a function of the dietary level of Try. The Try availability from FDA was 97.9% and 110.5% using the decrease and the slope criteria respectively.

¹ Published as Paper Number 4091. Journal Series, Nebraska Agricultural Experiment Station.

² Department of Animal Science. Acknowledgement is made to John Welch and Barbara Petersen for their laboratory assistance and to Dawes Laboratories Inc., Chicago, Illinois and American Cyanamid Co., Princeton, New Jersey for product support of the research.