Tryptophan Requirement of Early-Weaned Pigs from Three to Seven Weeks of Age

Abstract

Four experiments were conducted to study the tryptophan requirement of the 21- to 45-day-old pig. The first two experiments utilized a corn-zein-fish meal diet containing 20% protein. Highest rates of gain and feed efficiency were obtained at tryptophan levels of 0.17 to 0.19%. The third trial utilized intact casein and casein hydrolysate as protein sources. A tryptophan level of 0.16% in a 16% protein diet containing intact casein as the only source of protein produced the highest rate of gain and efficiency of feed utilization. When half of the casein was replaced by casein hydrolysate supplemented with asparagine, methionine and NaHCO3, the level of performance at 0.16% tryptophan was reduced significantly. When the tryptophan requirement was studied at two protein levels in corn-fish meal diets, gains in a 16% protein diet were not significantly improved at tryptophan levels higher than 0.14%. However, in agreement with the previous trials, average daily gain was consistently greater at tryptophan levels up to 0.18% of the diet. A tryptophan level of 0.18 to 0.22% of a diet containing 20% protein is suggested as a minimum requirement for optimal performance of the 21- to 45-day-old pig fed non-purified diets. The tryptophan requirement for pigs of this age appears to be approximately 1% of the dietary protein.