Abstract
Three experiments were conducted to estimate the lysine requirement of the weanling pig and the effects of excess arginine and threonine on- that estimate. Feeding 1.15% dietary lysine in Exp. 1 and 1.20% in Exp. 2 maximized feed efficiency and resulted in the lowest plasma urea N values. Adding .15% threonine to the diets in Exp. 2 did not affect (P>.10) performance of the pigs, but increased (P<.01) plasma urea N and decreased (P<.01) plasma lysine concentrations. Supplemental arginine (.22%) did not affect performance of the growing pigs in Exp. 3, but it increased (P<.01) plasma urea N. Pigs fed a corn-soybean meal diet utilized feed more efficiently (P<.05) than those fed a corn-fish meal-dried whey diet. The most likely cause for this response was that the corn-soybean diet contained more lysine (.82%) than expected, whereas the corn-fish meal-dried whey diet had close to the expected content of lysine (.72%). From these results, it was concluded that the lysine requirement of the weanling pig fed practical diets is at least 1.15 or 1.20% of the diet. Also, added arginine or threonine did not adversely affect the performance of pigs. Copyright © 1984. American Society of Animal Science. Copyright 1984 by American Society of Animal Science.