Abstract
Pigs averaging about 5.9 kg initially were fed diets providing 0.45, 0.60 and 0.75% isoleucine and 0.70, 0.78, 0.86, 0.94 and 1.02% leucine in a factorial arrangement of treatments. There was a trend toward decreased daily gain with increasing leucine content of the diet. Level of dietary leucine exerted significant quadratic effects on gain/feed and on gain/protein (protein efficiency ratio or PER) with means being depressed at intermediate levels of leucine intake. Level of dietary isoleucine did not affect average daily gain, gain/feed or PER significantly and there were no isoleucine X; leucine interactions for these response criteria. Level of dietary leucine exerted highly significant (P<.01) linear and quadratic effects on the concentrations of plasma free isoleucine, leucine and valine. Levels of plasma free leucine increased with increasing dietary leucine while the concentrations of both plasma free isoleucine and valine decreased. Levels of plasma free isoleucine increased with increasing dietary isoleucine and there was an isoleucine X; leucine interaction for plasma free isoleucine, but not for either leucine or valine. Time of sampling did not affect the concentrations of the three free amino acids in the plasma and there were no time of sampling X; treatment interactions for these response criteria. Copyright © 1973. American Society of Animal Science . Copyright 1973 by American Society of Animal Science