Effects of vitamin A and β-carotene injection on levels of vitamin E and on glutathione peroxidase activity in pregnant Tuj sheep

The objective of research was to study the effect of vitamin A and beta-carotene injections, before breeding and during pregnancy, on the levels of vitamin E in plasma and on the activity of erythrocyte glutathione peroxidase (GSH-Px) in sheep. Thirty-two healthy female and four healthy male Tuj sheep, 4-5 years old and weighing approximately 57 kg each, were used. The female animals were divided into 4 groups with 8 sheep in each. The oestrus cycles of the ewes were synchronised by the application of sponges containing medroxyprogesterone acetate (MPA) and by the intramuscular administration of 500 IU of PMSG. Twenty-four hours after the injection of PMSG, a ram was added to each group and allowed to mate with the sheep. The first group was used as the control. 8 mg/kg of beta-carotene (Group II), 200,000 IU of vitamin A (Group III) and a combination of 100,000 IU of vitamin A and 4 mg/kg of beta-carotene (Group IV) were administered intramuscularly at 30-day intervals, 15 days before breeding and during pregnancy. To measure the levels of vitamin E in plasma and the activity of erythrocyte GSH-Px, blood samples were taken from the jugular vein on days 1 and 15 after injection and after the birth. A statistically significant difference (P < 0.001) was observed during pregnancy in the levels of vitamin E in the plasma of Groups I I and IV following injection in comparison with those of the control group. It was also observed that vitamin E levels changed in the treated groups in relation to the time of injection. We further determined that the levels of vitamin E in plasma were little affected by injections of vitamin A. Erythrocyte GSH-Px activity increased in Groups II, III and IV compared with that of the control group (P < 0.001). This increase was higher in the beta-carotene group than in the other groups. It was concluded that supporting aspects of the antioxidant system such as vitamin E levels and GSH-Px activity with vitamin A and beta-carotene injections may prevent the undesired effects of the free radicals associated with pregnancy.