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 0.6 g/1 (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/1 (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/1 (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).

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Urinary nitrogen compounds were determined in test cows with urea as the sole (0-cows) or partial (ULP-cows) source of nitrogen. An average of 0.49 % total nitrogen was found in 0-cows and 0.88 % in ULP-cows, the values for urea nitrogen being 2.24 and 2.63 mg/ml, for ammonium nitrogen 0.14 and 0.09 mg/ml, for creatinine 0.77 and 0.90 mg/ml and for creatine 0.28 and 0,42 mg/ml urine, respectively. Differences between the two groups were highly significant (P < 0.001) as regards total nitrogen and significant (P < 0.05) as regards urea nitrogen and creatine. In each group the between-cow differences were highly significant with regard to total and urea nitrogen and creatine, and in 0-cows also with regard to ammonium nitrogen and creatinine. Smaller amounts of urinary allantoin and larger amounts of uric acid were found in 0-cows than in ULP-cows. Corresponding determinations were made to some extent also on the urine of cows on normal indoor or pasture feeding.

Abstract. The nitrogen compounds of the faeces of dairy cows on purified, proteinfree feed with urea and small amounts of ammcnium salts as the sole source of nitrogen (0-feed). on low-protein feed in which part of the protein was replaced with urea (ULPfeed) and on normal protein-containing feed (NorP-feed) were studied.The total nitrogen contents of the dry matter of the faeces were 2.5 dr 0.7 % on 0-feed, 2.4 dr 0.4 % on ULP-feed and 2.3 dr 0.6 % on NorP-feed. The proportion of urea-and ammonium nitrogen of the total nitrogen was 3.2 dr 2.4, 4.5 d: 2.4 and 3.7 dr 1.8 % respectively, and the proportion of nitrogen soluble in 70 % ethanol 10.9 dr 5.7, 9.9 ± 2.4 and 10.4 dr 3.8 % of the total nitrogen; the proportion of nitrogen in the free amino acid fraction was 4.1 d: 2.9 on 0-feed, 1.6 dr 1.4 (P < 0.05) on ULP-feed and 3.2 dr 2.9 % on NorP-feed.The nitrogen insoluble in 70 % ethanol as a proportion of the total nitrogen was 82.3 ± 7.2 on 0-feed, 85.4 dr 5.0 on ULP-feed and 82.3 dr 7.2 % on NorP-feed.Of the total nitrogen of this insoluble fraction, the following proportions were released as amino acids by acid hydrolysis: 62.15 ± 8.5 % on 0-feed, 61.6 d; 10.7 % on ULP-feed and 59.0 ± 13.9 % on NorP-feed. (t, e-diaminopimelic acid was 1.7 ± 0.6, 0.7 ± 0.2 (P < 0.05) and 1.2 ± 0,4 mol % respectively of the total amino acids of the hydrolyzate.The soluble nitrogen fraction was separated into free amino acid and »peptide» fractions, and the amino acid composition of both was determined, the latter after acid hydrolysis.