Effect of vitamin E on the immune system of ewes during late pregnancy and lactation

The present experiment was designed to determine the effects of a regimen of repeated, intramuscular (i.m.) injections of vitamin E (VE) on innate and humoral components of the immune response of pregnant and lactating ewes. Pregnant ewes were randomly assigned to two treatments consisting of i.m. injections of either VE (30 IU d- -tocopherol/kg BW, n = 10) or equivalent volume of a placebo (emulsified base, n = 8). Injections were administered at 2-week (wk) intervals to all ewes, as a group, for a total of 24 wk. Lambing occurred over a 5-wk period, starting wk 7 of the study. All ewes were administered a booster vaccination for Clostridium tetani and Clostridium perfringens (C + D) at wk 3. Blood and colostrum were analyzed for -tocopherol and selenium content, and extracellular glutathione peroxidase (GPX3) activity as measures of antioxidant status; lysozyme activity as a measure of innate immunity and immunoglobulin G (IgG), and anti-tetanus toxoid IgG (IgG-T) concentration as a measure of humoral immune status. Three ewes in the placebo group did not lamb and were therefore excluded from all analyses. Results showed a significant treatment × week effect of VE supplementation on IgG concentration. VE supplementation increased IgG concentrations in ewes after their yearly booster vaccination against C. tetani and C. perfringens; placebo-treated ewes showed no such response. The extent, magnitude and persistence of the decreased IgG concentration during the transition period were less in VE-supplemented ewes than controls. There was no effect of VE supplementation on the concentration of IgG-T after vaccination. VE-supplementation of pregnant ewes had no effect on serum lysozyme activity. GPX3 increased in both treatment groups, peaking during the transition period. The -tocopherol content of the colostrum of VE-supplemented ewes was greater than that of controls. In conclusion, VE supplementation of pregnant and lactating ewes had an equivocal effect on variables used to assess immune function. The benefit of VE supplementation to pregnant and lactating ewes requires further research however it may have utility in blunting the immune suppression that occurs during the transition period.