Abstract
A linear relationship between the amount of allantoin excreted in the urine of cattle and the digestible dry-matter intake, has been found for cattle fed different roughage diets. The relation was also linear for buffalo although they excreted less urinary allantoin than cattle at the same level of digestible dry matter intake. It is postulated that the relationship arises because of the contribution that degraded microbial nucleic acids make to the excreted allantoin in the urine of cattle.