The effect of feeding on the hippuric acid content of cow’s urine

Authors

• M. Kreula Biochemical Research Institute, Kalevankatu 56 B, 00180 Helsinki 18
• A. Rauramaa Biochemical Research Institute, Kalevankatu 56 B, 00180 Helsinki 18
• T. Ettala Biochemical Research Institute, Kalevankatu 56 B, 00180 Helsinki 18

DOI: https://doi.org/10.23986/afsci.71987

Abstract

The urinary hippuric acid contents of dairy cows on a purified, proteinfree feed (0-feed, 0-cows), as well as the effect of benzoic acid and aromatic amino acid supplements, and silage and hay supplements, on the urinary hippuric acid content, were followed in the present study. The hippuric acid contents of the urine of 0-cows were compared with those of a cow on low-protein, urea-rich feed containing hemicellulose (ULP-cow). and of normally-fed cows (NorP-cows). The urinary hippuric acid content of the 0-cows varied between 0.1 and 0.6g/l (n = 8). The proportion of hippuric acid nitrogen of the total urinary nitrogen was 0.2—0.9 %. The presence of hippuric acid in the urine of the 0-cows indicates an endogenic hippuric acid production within the cow. 0-feed is deficient in all exogenic precursors of benzoic acid. Addition of benzoic acid to the feed of 0-cow caused temporary rise in the hippuric acid contents of the urine, of aromatic amino acids the addition of tyrosine, besides benzoic acid, raised the urinary hippuric acid content by a highly significant amount. The urinary hippuric acid content of the ULP-cow was on average 6.7 g/l (n = 42) and the proportion of hippuric acid on the total urinary nitrogen 5.2 %. The urinary hippuric acid contents of the NorP-cows were on average 11.9 g/l (n = 14), and the proportion of hippuric acid nitrogen of the total urinary nitrogen 10.7%. The difference in the urinary hippuric acid contents with 0- and NorP-cows is significant, as is also the difference in the proportions of hippuric acid nitrogen of the total urinary nitrogen with these cows. The difference in the hippuric acid contents of 0- and ULP-cows is also significant (P < 0.01). The same regards ULP- and NorP-cows (P < 0.01).