Effect of Supplemental Vitamin E and β-Carotene on Cell-Mediated Immunity and Mastitis in Crossbred Cows

Crossbred pregnant cows (18) in their late lactation were divided into three equal groups and fed as per standard feeding practices. Cows of groups I, II and III were supplemented with 0, 1000 mg α-tocopheryl acetate and 1000 mg α-tocopheryl acetate plus 300 mg β-carotene, respectively from 45 d prepartum to 120 d postpartum. Lymphocyte proliferation assay for evaluating the cell-mediated immunity (CMI) was carried at one week prepartum, calving and one week postpartum. Incidence of sub-clinical mastitis (SCM) was assessed before drying off and fortnightly during 120 d postpartum. Plasma α-tocopherol and retinol levels decreased significantly at calving in all the groups, but the decrease was less in cows of groups II and III as compared to group I. However, group II and III cows returned to normal levels earlier than control cows. Percent decrease in CMI was 47.9, 31.9 and 31.5 at parturition which increased by 41.2, 85.5 and 37.4% during postpartum period in the three groups respectively. Maximum increase in CMI after parturition was observed in vitamin E supplemented group II. The incidence of SCM before drying off was observed with percentage of infected teats as 36, 50 and 36 in the three groups, respectively. Within one week of parturition, percentage of infected teats was 52, 8 and 9 in groups I, II and III, respectively. The increase in the percent infected quarters at parturition in group I indicated the development of new infections besides persistence of previous infections during drying off period. Percent teat infection averaged 26.51, 20.41 and 12.49 in the three groups, respectively. The incidence of clinical mastitis within one week of parturition decreased by 66.6% in groups II and III. The results highligh the beneficial effects of supplementing vitamin E and β-carotene on mastitis in periparturient cows.