Valine requirement of the growing kitten.

The valine requirement of the kitten was studied using a crossover design with two groups of three weanling kittens. The kittens were fed a semipurified diet containing only free amino acids as a source of nitrogen containing 0.0%, 0.6%, or 1.8% valine. The mean +/- SE of the linear components of growth (g/day) of the six kittens were respectively:-13.8 +/- 1.7, 17.3 +/- 4.8, and 15.3 +/- 2.6. Corresponding food intakes were 26.0 +/- 3.9, 50.4 +/- 2.5, and 44.0 +/- 1.5. Nitrogen balance was positive with the same amount retained for the two valine-containing diets while nitrogen balance was negative for the kittens fed the valine-free diet. Plasms valine dropped markedly when the dietary valine was decreased from 1.8% to 0.6% (363 +/- 59 versus 66 +/- 13 nmole/ml), and was further decreased (33 +/- 13) when the valine-free diet was fed. It does not appear that the valine requirement of the kitten exceeds 0.6% of a diet containing 25% fat. These results support the hypothesis that the high protein requirement of the kitten is not a result of a high requirement for all the essential amino acids, but a result of a high "nitrogen" requirement.