COMPARISON OF KETOSIS, CLINICAL MASTITIS, SOMATIC-CELL COUNT, AND REPRODUCTIVE-PERFORMANCE BETWEEN FREE STALL AND TIE STALL BARNS IN NORWEGIAN DAIRY HERDS WITH AUTOMATIC FEEDING

Differences in ketosis and clinical mastitis rates, mean somatic cell counts (SCC) and reproductive performance scores (fertility status ind ex = FS-index) between herds housed in free stall (n = 533) and tie st all (n = 59) barns were measured in relation to management and environ mental factors in a retrospective cohort study of Norwegian dairy farm s with automatic grain feeding systems. Herds with tie stalls were fou nd to have a higher clinical mastitis rate, (61.6 cases per 100 cow-ye ars versus 46.4 cases per 100 cow-years (p<0.01)); a significantly hig her proportion of herds with ketosis, (relative risk = 1.59, (p<0.01)) ; and a lower mean fertility status index, (67.3 versus 82.8 (p<0.01)) . No significant difference in mean SCC was found between the 2 groups of dairies (p = 0.32). Large herds had higher Log(e) geometric mean S CC than small herds (p<0.01) and herds with high SCC had lower milk pr oduction than herds with low SCC (p<0.01). Herds that scored ''very go od'' on cow cleanliness had significantly lower adjusted mean SCC than herds with scores of ''average'' or ''good'' (p<0.05). Herds in barns with a concrete floor had an adjusted mean number of cases of clinica l mastitis of 51.4 per 100 cow-years, 14 per cent higher than herds in barns with rubber mats, litter bed or wood (45.2 cases per 100 cow-ye ars) (p<0.05). Herds with high milk production level had higher FS-ind ex than herds with low milk production (p<0.01). Lower disease rates a nd the higher fertility status measured in the present study favor fre e stall herds over tie stall herds.