Relationship between Concentrations of Ruminal Nucleic Acids and Excretion of Purine Derivatives by Sheep

Abstract

PURINES can be synthesized in the animal body from glycine, serine, aspartic acid, glutamine, formate and respiratory carbon dioxide, but they are also derived from dietary and cellular nucleoprotein. Recent work with cattle1 and sheep2 has shown that purine derivatives (uric acid and allantoin in urine) are quantitatively important end-products of these ruminants when they are fed on diets with a high-energy, low-protein content and when the animals are in either N equilibrium or slight positive balance. With such diets protein is utilized very efficiently. It is well known that efficiency of protein utilization in the ruminant depends on the catabolic and synthetic activities of the rumen micro-organisms. For high efficiency, the breakdown products of dietary protein and other nitrogenous compounds must be rapidly synthesized into microbial protein in the rumen3. This evidence suggests that most of the allantoin and uric acid excreted by ruminants may be derived from nucleic acids of rumen micro-organisms. Some support for this suggestion has been reported by Blaxter and Martin4, who showed that after ruminal infusion of casein (which is free of purine and pyrimidine bases) slightly more allantoin was excreted than after abomasal infusion of the same quantity of casein.