Studies on the incidence of clinical mastitis and blood levels of vitamin E and selenium in dairy herds in England.

In a trial conducted in the south of England in January to February 1989, blood samples were obtained from nine dairy herds with more than 30 cases of clinical mastitis/100 cows and from nine herds with less than 30 cases/100 cows during the previous 12 months. Whole blood glutathione peroxidase (GSHPx) activity and plasma vitamin E concentration were determined for 12 cows in each herd. The mean (+/-sd) values for the herds with the lower incidence of mastitis were 7.57 +/- 1.86 micrograms/ml plasma vitamin E and 23.8 +/- 22.8 U/ml rbc GSHPx activity, compared with 7.74 +/- 1.69 micrograms/ml plasma vitamin E and 20.61 +/- 8.8 U/ml rbc GSHPx activity for the herds with the higher incidence of the disease. These values indicate that the vitamin E levels were generally adequate but that some animals and herds had low GSHPx activities, suggesting that their diets may have contained inadequate selenium. The activities of GSHPx and the vitamin E levels in plasma were not significantly different in the two groups of herds, and no relationship was found between the two nutrients and the incidence of clinical mastitis. However, there was a significant negative correlation between the activity of GSHPx and the bulk milk cell counts in the herds with a low incidence of mastitis suggesting that there was an association between the incidence of subclinical mastitis or inflammation and the selenium status of these herds.