Effect of pre and postpartum maternal supplementation of zinc and selenium via slow-release glass bolus or the element salts on feed intake and some blood parameters in ewes and their lambs

Abstract

In late pregnancy and early lactation, ewe^'s demand increases for zinc (Zn), and selenium (Se) for scavenging of free radicals and due to transfer via placenta, colostrum or milk to lamb.This experiment was conducted to study the effect of slow-release bolus of Zn and Se on performance, and some blood parameters of pregnant ewes in the last third of pregnancy, and early lactation as well as their lambs. Twenty-one ewes were estrus synchronized in the breeding season by intra vaginal insertion of sponge containing medroxyprogesterone acetate. Forty-five days before the expected date of parturition, the pregnant ewes (3–4 years old and 55±5.2 kg in weight) were randomly assigned to one of the three groups: 1) control, 2) slow-release glass bolus with mean release of 20 mg Zn and 0.2 mg Se per day (Bolus), and 3) 20 mg Zn and 0.2 mg Se per day as sulfate and selenite, respectively via Daily feeding (Daily). Blood samples were obtained from ewes at 105th and 135th days of pregnancy, at parturition and 15th day postpartum and from lambs at 15 days of age. The results indicated that total feed intake of ewes increased (P = 0.03) in the Bolus and Daily groups than control. Supplementation of Zn and Se in both methodssignificantly increased Total Antioxidant Capacity (TAC) in the ewesand their lambs than the control group. Compared with the control, there was higher triiodothyronine (T₃) in ewes and their lambs and lower tetraiodothyronine (T₄) only in lambs in Bolus and Dailygroups. Increased T₃ to T₄ ratio in ewes (at days 135 of pregnancy and at parturition) and their lambs was recorded in Bolus and Daily than the control group. An increased level of alkalinephosphatase (ALP) in ewes was observed in the Bolus and Daily groups compared with the control. Alanine amino transferase (ALT) activity on day 135 of pregnancy was significantly reduced by Zn and Se supplementation in both methods. Bolus and Daily groups of ewes had lower creatinephosphokinase (CPK), and their lambs had lower aspartate amino transferase (AST), ALT, CPK, and gamma-glutamyltransferase (GGT) than the control group. Regardless of the supplementation method, Zn and Se increased glucose (P = 0.02) and decreased triglyceride (P = 0.06) in ewes. In the ewes supplemented with Zn and Se, creatinine concentration significantly decreased in parturition day compared to control. Total protein, albumin, globulin and ratio of albumin to globulin in ewes and their lambs were not different between treatments. As a result, Zn and Se improved antioxidant status and some blood parameters in ewes and their lambs. Efficacy of slow-release bolus of Zn and Se was similar with daily feeding of these elements.