搾乳設備の異常が乳房衛生に及ぼす影響

Three experiments were conducted to ensure the effects of milking machine deformities, high vacuum (40cmHg=53.3kPa) and faulty pulsation on somatic cell count (SCC) and electrical conductivity (EC) of milk. The first experiment was carried out to examine the influence of abnormal high vacuum for 3 weeks, by comparison with that of the normal one (35cmHg=6.7kPa). In the second experiment, the influence of milking under faulty conditions in pulsator ratio and shifting speed of phases was examined for 3 weeks. And, the third experiment was undertaken for 3 weeks to examine the effect of milking under the condition combined with high vacuum and faulty pulsation on SCC and EC. There were several weeks for recovery and control periods before each experiment. An analysis of data was made due to the following two methods: (1) After all quarters were classified into four groups on the basis of their infectious status and SCC level measured during the control periods, the analysis of variance technique was applied to the data from four groups, respectively. The four groups were one group consisting of infected quarters with major pathogens and the other three groups consisting of non-infected quarters with three difference levels of SCC. (2) Analysis of variance in a nested design was made on the difference calculated by subtracting the value at control period from that at treatment period.<br>A significant increase in SCC for the infectious quarters group (1) and low SCC level quarters group (4) was found when high vacuum treatment was applied. Although no influence of faulty pulsation treatment appeared in any group, when high vacuum and faulty pulsation treatment were combined, difference in SCC between treatment and control period was significant in all groups except for one with quarters producing milk with 200-500 thousands cells/ml. On the other hand, no significant difference was found in EC for all groups except for the infectious quarters group (1) where an increase in EC was found under high vacuum and faulty pulsation treatment. The result of analysis of variance in the nested design showed that the degree of influence of milking machine deformities on EC is greater among individual cows than among quarters, while the influence on SCC was found among individual cows as well as among quarters. It was suggested that milking machine deformities employed in the present experiments had a greater influence on SCC than EC.