A total of 119 raw milk samples from ten dairy farms were examined for total bacterial count, and 739 quarter milk samples of 118 dairy cows of 14 herds were examined for mastitis. The results obtained were as follows:
1. The mean of total bacterial counts of the 119 raw milk samples was 132,000 per ㎖. The total bacterial counts of 81 samples (68.1%) were under the standard of 100,000 per ㎖ and those of the 38 samples (31.9%) were over the standard. The number of bacteria showed a tendency to increase in summer.
2. One hundred and ninety five quarters (26.4%) of 98 cows (52.7%) were proved to be infected with mastitis. Clinical mastitis was found at 7 quarters (3.5%) of 5 cows (5.0%).
3. Staphylococcus (44.9%) and Streptococcus (26.7%) were two main causative organisms of mastitis. Coliform bacteria (4.6%), Pseuedomonas spp. (4.6%), yeasts (1.3%) and corynebacterium sp. (0.7%) were also isolated from the infected quarters.
4. The isolates were more sensitive to chloramphenicol ((96.1%), leukomycin (78.8%), streptomycin (75.5%) and tetracycline (72.4%). On the other hand, they were less sensitive to colistin (11.0%), oreandomycin (18.1%), sulfisoxazole (24.6%), penicilline (27.6%), kanamycin (43.3%) and erythromycin (49.7%). Especially the strains of Pseudomonas spp. isolated from the infected quarters were resistant to almost all the drugs examined.
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