KITTENS CHOOSE A HIGH LEUCINE DIET EVEN WHEN ISOLEUCINE AND VALINE ARE THE LIMITING AMINO-ACIDS

This study was conducted to determine the effect of excess leucine on the dietary choice of kittens. The basal diets contained 16% (low nitr ogen) or 24% (adequate nitrogen) amino acids and were limiting in isol eucine and valine. The addition of leucine to either of these basal di ets has been shown to cause a transitory adverse effect on the growth and food intake of kittens. In separate experiments each basal diet wa s used to test three sets of choices: basal vs. basal + 10% leucine; b asal + alanine vs. basal + leucine (isonitrogenous) and basal vs. basa l + alanine. When offered basal vs. basal + excess leucine, the kitten s chose significantly more of the excess leucine diet regardless of th e level of nitrogen in the basal diet. When offered an isonitrogenous choice of excess alanine vs. excess leucine, the kittens selected some what more of the excess leucine diets over the excess alanine diets; t his selection was sustained longer in kittens fed low nitrogen. In the third choice experiment (basal vs. basal + alanine), the group offere d the low nitrogen diets exhibited no preferences, and the group offer ed adequate-nitrogen diets selected significantly more of the excess a lanine diet. These results for kittens are opposite to those for rats, a species that will select a low protein basal or even a protein-free diet over a diet containing excess leucine.