This study was carried out to determine the effects of vitamin E on levels of plasma and milk vitamin A, beta carotene (β-carotene), glutahione peroxidase (GSH-Px) and reduced glutathione (GSH) in subclinical mastitic dairy cows. Forty cows were assigned to two groups by the use of California Mastitis Test (CMT) and somatic cell count (SCC). Vitamin E (2.000 IU) was injected to cows of mastitic group by intramuscular route overnight for twenty days. The plasma and milk samples of the cows in healthy, pre- treatment and post-treatment mastitic groups were analyzed.

The levels of vitamin A, β carotene, GSH-Px and GSH in plasma and vitamin A level in milk were determined. Differences in plasma vitamin A (P<0.05), β-carotene (P<0.01), GSH-Px (P<0.01), GSH (P<0.001) and milk vitamin A (P<0.001) values between healthy and mastitic pre-treatment groups were significant. Differences in plasma vitamin A (P<0.05), GSH (P<0.001) and milk vitamin A values (P<0.01) were found as stastistically significant whereas these in plasma β-carotene and GSH-Px values (P>0.05) were not significant between pre-treatment and post-treatment mastitic groups