Effect of administration of vitamin E and selenium during the dry period on mammary health and milk cell counts in dairy ewes

The effect of parenteral administration of two subcutaneous injections of vitamin E and Se (5 mg and 0.1 mg/kg of body weight, respectively) during the dry period on the mammary health and milk somatic cell counts of 25 dairy ewes was investigated. Supplementation reduced somatic cell counts (5.4 vs. 6.0 log10) during the subsequent lactation but had no effect on the incidence of clinical mastitis (4% vs. 6%) and intramammary infections (9.0% vs. 11.3%). Furthermore, the administration of vitamin E and Se was associated with differences in differential cell counts of milk samples (macrophages, 48.8% vs. 38.4%; polymorphonuclear neutrophils, 40.1% vs. 50.7%; and eosinophils, 0.7% vs. 1.4% for control ewes and ewes receiving supplements, respectively). The administration of these supplements also increased erythrocyte glutathione peroxidase activity (139.5 vs. 86.3 U/ml of packed cell volume) and the percentage of blood neutrophils that reduced nitroblue tetrazolium after bacterial extract stimulation (48.6% vs. 38.7%). Parenteral administration of vitamin E and Se to ewes during the dry period appeared to have influenced mammary gland status during the subsequent lactation and particularly total and differential milk cell counts. ( Key words: vitamin E, selenium, somatic cell count, dairy ewes)