PREDICTION OF THE EXCRETION OF ALLANTOIN AND TOTAL PURINE DERIVATIVESBY SHEEP FROM THE CREATININE COEFFICIENTS

The urinary excretions of creatinine, allantoin and total purine deriv atives by Merino ewes were compared with predictions based on the assu mptions that creatinine excretion scaled to liveweight (the creatinine coefficient) was constant and was not affected by diet. The creatinin e coefficient varied between individuals and was found to be affected by diet (P < 0.01). As a result, there were systematic deviations (P < 0.01) in the predictions of allantoin and total purine derivative exc retion. If predictions of purine derivative excretion are to be made f or individual animals in the absence of total urine collections, prior determination of individual creatinine coefficients is required and p redictions may be confounded by diet effects on creatinine excretion. Predictions for groups on the basis of general relationships between t he creatinine coefficient and liveweight may be subject to errors betw een diets of > 10%.