Summary Possible sources of exogenous contamination of raw milk by Listeria monocytogenes were examined on four dairy farms of different size and type of animal housing during morning milking. Feeds, including hay and concentrates, were found to be major sources of both pathogenic and nonpathogenic species of Listeria on the barns. L. innocua was the only species isolated from the grass silage, which was of good quality on all the farms. The numbers of Listeria were below 102/g in all feed samples. Fecal shedding of listeriae was detected in 11.9% of the cows and the prevalences of L. monocytogenes among farms ranged from no detections to 8.7 %. The number of Listeria isolations from constructions inside the barns and from the milking environment varied between the farms. Listeriae were detected almost everywhere on one of the farms whereas on another farm the only isolations were from feed passages and floors. 13.6 % of the swab samples taken from the teats before washing and drying were Listeria positive, whereas no isolations were made after cleaning the udder. Good milking and barn hygiene is considered important for diminishing the risks of exogenous contamination of raw milk by listeriae.

Abstract. The effect of the inoculation and the adding of the cellulase enzyme on the fermentation of sugar-rich, direct cut grass were studied. The control silages were made by using AIV II solution and no additives. The silages were prepared from the first cut on a farm scale in the summer of 1985.Generally all four silages were organoleptically good. The results showed only minor differences in the fermentation between untreated and inoculated or enzyme silages. The quality of fermentation, however, was improved in inoculated and enzyme silages. The quality further improved by using the AIV II solution. This was supported by the changes in the pH, ammonia, buffering capacity, redox potential, temperature and finally by a better digestibility of organic matter.

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).

The occurrence of Listeria spp. in pasture grass and grass silage made with various additives and preservation techniques is reported. Silage samples were collected three times (in November, February and May) from eighty dairy farms. The prevalence of Listeria spp. in pasture grass samples was 0-647 and in silage samples 0-227. Only two species, L. monocytogenes and L. innocua were observed. Listeria spp. were isolated from the silage at least once at thirtynine farms (0-488), and L. monocytogenes at twenty-seven farms (0-338). The occurrence of Listeria was highest among the silage samples collected in November (0-288). Silages preserved with acids had the lowest prevalence of Listeria (0-194). Silages preserved in tower silos were most often free of Listeria, only 0-056 being positive. The highest prevalence of the Listeria spp. (0-324) was detected in clamp silage. The results of chemical analyses of silage statistically reflect the frequency of Listeria.

Abstract. 6 cows were fed for 2 weeks with fresh cut grass treated with formaldehyde-containing preservative. The formaldehyde content of the treated grass, as fed, averaged 490 mg/kg fresh weight and the consumption was 32 -44 kg fresh material/ cow/day. The formaldehyde content of the milk rose rapidly from a pre-feed level of 0 to 0.6 -2.2 mg/kg, and fell to 0 immediately after the feeding period. The faeces and urine contained 150 260 and 16 -26 mg formaldehyde/kg fresh weight respectively during the feeding period, background values being about 10 and 1 mg/kg.