The Effect of Slow-Release Bolus of Zinc and Selenium or Daily Feeding of Salts of These Elements on the Performance of Pregnant Ewes and Their Lambs

The aim of this study was to evaluate effect of zinc and selenium slow-release bolus and compared to daily feeding of these elements in late pregnancy and early lactation on performance of ewes and their lambs. In the breeding season, 21 non-pregnant ewes of Mehraban breed with an average weight of 55 ± 5.2 kg and a body score of 2.5-3 were estrus synchronized using sponge. At the time of sponge removal, all ewes received 400 international units of PMSG (pregnant mare serum gonadotropin) and then crossbred with Afshar-Brola rams. 45 days before the expected date of parturition date, pregnant ewes were assigned to one of these three groups: 1) control treatment, 2) treatment of 20 mg of zinc and 0.2 mg of selenium per day in the form of a slow release bolus, 3) treatment of 20 mg of zinc and 0.2 mg of selenium per day in the form of daily feeding of salt of these elements. Zinc and selenium supplementation in both methods increases plasma zinc and selenium concentrations and the activity of glutathione peroxidase and superoxide dismutase enzymes of ewes on all test days and increased zinc and selenium concentrations in colostrum and milk (P <0.05). The amount of hemoglobin and the number of red blood cells in both groups of ewes receiving zinc and selenium were higher than the control group (P <0.05). In both groups of ewes receiving zinc and selenium, plasma concentrations of these elements and glutathione peroxidase activity increased compared to control. Maternal supplementation of zinc and selenium in both methods increased the weight of 20 and 30 days and daily weight (21 to 30 days) of lambs. In general, zinc and selenium supplementation increased the plasma concentrations of these elements and the activity of antioxidant enzymes in ewes and their lambs and improved the growth performance of lambs. No differences were observed between the two methods of blues and daily feeding. Therefore, blouses are recommended due to their ease of use.