The level of dietary protein affects the vitamin B-6 requirement of cats.

A depletion-repletion model was used to study the effect of the level of dietary protein on the vitamin B-6 requirement of growing kittens. Twenty kittens were given a pyridoxine-free diet for 42 d to deplete vitamin B-6 reserves. They then were divided into four groups of five kittens each. Two groups were fed diets containing 30% casein with either 1.0 (Group 30-1) or 2.0 (Group 30-2) mg pyridoxine/kg diet and two groups were fed 60% casein diets with either 1.0 (Group 60-1) or 2.0 (Group 60-2) mg pyridoxine/kg diet for 44 d. During repletion, body weight gain of kittens from Group 30-2 was higher than that of kittens from the other groups. Body weight gains of kittens from Groups 30-1 and 60-2 were higher than that of kittens from Group 60-1, but there was no difference in body weight gain between Groups 30-1 and 60-2. At 44 d of repletion, kittens from Group 60-1 generally had higher plasma concentrations of free tyrosine and cystathionine, lower plasma B-6 vitamin concentrations and a higher urinary oxalate excretion than did kittens from the other groups. These findings indicate that the vitamin B-6 requirement of growing kittens--as is true of humans, chickens and mice--is positively related to the level of protein in the diet. For a 30% casein diet, the vitamin B-6 requirement was greater than or equal to 1.0 but less than 2.0 mg pyridoxine/kg diet; for a 60% casein diet, the requirement was greater than or equal to 2.0 mg pyridoxine/kg diet.