RESPONSE OF RENAL OROTIC-ACID AND CREATININE TO TREATMENTS AFFECTING METABOLIC PROTEIN SUPPLY OF RUMINANTS

90 urine samples obtained in three lamb trials and one experiment usin g adult wethers were analyzed for their contents of erotic acid and cr eatinine. The average daily excretion of erotic acid accounted for 0.5 mg to 1.5 mg (35 mu g to 130 mu g/W-0.75 ) with a high individual var iation. Correlation coefficients between erotic acid and other urinary constituents were low indicating an entirely different response to me tabolic variations, There was only a weak relationship to live weight, protein retention and rumen fluid traits. Defaunation reduced the ero tic acid excretion (significant in the adult wethers) whereas the addi tion of rumen-protected lysine as well as the use of different dietary carbohydrate sources were without effect. The urinary excretion of cr eatinine increased with live weight and age from 0.4 g/d in the 20 kg lambs to 1.7 g/d in the adult 53 kg wethers. The correlations with liv e weight were close whereas the apparently negative correlation with p rotein retention was not real as could be evaluated by calculation of the partial correlations. There was a close correlation of creatinine with total N, urea and allantoin. Neither defaunation nor rumen-protec ted lysine and the kind of carbohydrate source had significant effects on creatinine. The use of erotic acid and creatinine as indicators of metabolic disorders were discussed. Easy application in practical dia gnosis without quantitative urine collection might be possible by the determination of erotic acid in the milk of cows and of the creatinine /N ratio in urine.