The nitrogen requirement of the weanling kitten

The nitrogen requirement of the weanling kitten was determined in a series of three experiments. In each experiment, diets were formulated to provide the growing kitten with the essential amino acids at or above the level of requirement. Expt 1 utilized a 4 x 4 balanced Latin square design with two groups of kittens (four male and four female). The crystalline L-amino acid diets were presented at four levels of dietary crude protein (N X 6.25) of 140, 160, 180 and 200 g/kg diet. The design for Expts 2 and 3 was a 6 X 6 balanced Latin square. For each of these experiments, groups of six male and six female kittens were assigned to diets. The six levels of dietary crude protein were 120, 140, 160, 180, 200 and 220 g/kg diet; dietary N was supplied by crystalline L-amino acids for Expt 2 and casein plus a supplementary amino acid mix for Expt 3. Food intake, weight gain and N retention were determined in each experiment. A sigmoidal model y = P1 + P2/[1 + e(P3 + P4 X chi] was fitted to the response of weight gain and N retention to dietary N. The calculated requirement (95% of the upper asymptote, P1 + P2) for these experiments varied from 170 to 230 g protein/kg diet with the majority of these values falling between 180 and 200 g protein/kg. On the basis of these three experiments, the kitten's requirement for dietary crude protein is between 180 and 200 g/kg diet (28.8-32.0 gN/kg) for purified diets which provide a calculated 21 MJ metabolizable energy/kg diet.