Prediction of the excretion of allantoin and total purine derivatives by sheep from the ‘creatinine coefficient’

The urinary excretions of creatinine, allantoin and total purine derivatives by Merino ewes were compared with predictions based on the assumptions that creatinine excretion scaled to liveweight (the creatinine coefficient) was constant and was not affected by diet. The creatinine 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 excretion. If predictions of purine derivative excretion are to be made for individual animals in the absence of total urine collections, prior determination of individual creatinine coefficients is required and predictions may be confounded by diet effects on creatinine excretion. Predictions for groups on the basis of general relationships between the creatinine coefficient and liveweight may be subject to errors between diets of > 10%.