FURTHER-STUDIES ON ARGININE REQUIREMENT OF RABBIT

The arginine requirement of young, female rabbits was reassessed using body weight gain, serum arginine concentration and expired 14CO2 following administration of 14C arginine as criteria of adequacy. With a diet that provided the indispensable amino acids at the previously estimated requirement level the arginine requirement was estimated at or near 0.6% of diet by all 3 of the criteria studied. When an amino acid pattern based on isolated soy protein was fed, a significantly lower serum arginine level was observed with 0.6% dietary arginine corroborating that the arginine requirement may be higher when this pattern is fed than when the requirement pattern is fed. Liver arginase [EC 3.5.2.1] and kidney transamidinase [EC 2.1.4.1] levels were normal and were not influenced by dietary arginine levels over the range used. Serum creatine phosphokinase [EC 2.7.3.2], which has been studied in other species in relation to muscular dystrophy, showed a significant increase with increasing dietary level of arginine. No signs of this disorder, were observed. Adult male rabbits maintained body weight and showed no change in serum arginine concentration when both arginine and glycine were completely omitted from the diet.