Hydrogen peroxide produced by a low-molecular-weight compound in milk with high electrical conductivity in dairy cows.

In dairy cows, hydrogen peroxide (H(2)O(2)) produced from a low-molecular-weight compound in milk from inflamed quarters was lower than that in milk from un-inflamed quarters. In milk of delivery grade, characteristics of H(2)O(2) production in milk with high electrical conductivity (EC) were examined in this study. Milk samples were collected from a total of 230 cows at 1-month intervals, and the EC of skimmed milk was determined. Based on the highest and the lowest EC of a cow's quarter milk, the inter-quarter difference of >= 0.6 mS/cm (mean + t(0.01) SE) was taken as a high EC. Milk with high EC was found in 52 quarters. In cows with milk of high EC, H(2)O(2) production in milk with normal EC was higher than that in milk with high EC in the same animal but was lower than that in the control population. In milk with high EC, the decrease of H(2)O(2) production correlated with the increase in EC. The production of H(2)O(2) decreased in particular when the inter-quarter difference exceeded 0.8 mS/cm. In milk collected from the same quarter 1 month before, EC changed from normal to high, and H(2)O(2) production decreased. In milk from the other three quarters, EC remained normal and H(2)O(2) production remained unchanged. We concluded that milk with high EC appeared in low H(2)O(2)-producing cows. The results suggest that the degree of decrease in H(2)O(2) production reflects the extent of quarter abnormality.