Dietary crude protein increases slightly the requirement for threonine in kittens.

Previous work indicates that the essential amino acid requirements for kittens are not positively correlated with the concentration of dietary nitrogen as they are in other species. In the studies presented here, the interaction between graded levels of threonine and dietary crude protein was investigated. Dose-response curves were generated using six 4 x 4 Latin squares. Each square represented one concentration of threonine (4.0, 5.0, 6.0, 7.0, 9.0 or 12.0 g/kg diet) and four concentrations of crude protein (150, 200, 300 and 500 g/kg diet). Food intake, weight gain, nitrogen retention and plasma amino acids were measured. There was no strong positive relationship between the threonine requirement of kittens and dietary crude protein. Increasing crude protein when threonine was limiting in the diet increased growth and food intake under some conditions, whereas under other conditions food intake and growth were decreased in a manner consistent with an amino acid imbalance response. An additional experiment was done to verify some of these findings. The requirement for threonine was found to increase from 5.0 g/kg diet at 150 and 200 g crude protein/kg diet to 6.0 g/kg diet when crude protein was 300 or 500 g/kg diet. The requirement for crude protein in the kitten appears to be between 200 and 300 g/kg diet.