PSLBII-17 - Supplementation with organic versus inorganic selenium during pregnancy to support ewe and lamb health

Abstract: Selenium (Se) is essential for optimal ovine health and production, and sheep raised on Se-deficient soils can be vulnerable to Se deficiencies that can affect immune function. Organic or inorganic forms of Se supplementation can remedy these consequences. While inorganic Se is less costly, organic Se is more bioavailable and may be more efficient in providing Se to ewes and lambs. The objectives of this study were to determine how organic versus inorganic Se supplementation affects ewe Se status, Se transfer from ewes to lambs, and the antibody-mediated immune response and dermal hypersensitivity response (DHR) of ewes and their lambs. Dorset-Rideau ewes (n=100) were enrolled in a randomized complete block design study. From gestation day (gd) 110 to postpartum day (ppd) 50, ewes were fed either a Se-deficient diet and supplemented with no Se, 0.3 mg inorganic Se, or 0.3 mg or 0.6 mg organic Se. Sera were collected on gd 110, 130, 140, and ppd 10 and 50 to determine ewe Se status. On gd 110 and 120, ewes received an intramuscular injection of 0.5 mg ovalbumin (OVA) antigen, and on gd 130 the DHR to OVA was assessed by measuring change in skinfold thickness 0, 6, 24 and 48 hours post intradermal injection. To measure the transfer of Se from ewe to lamb, a subset of lambs was euthanized at ppd 10, and longissimus dorsi muscle samples were collected and analyzed for Se content. On ppd 20 and 30, lambs received an intramuscular injection of 0.5 mg hen egg white lysozyme (HEWL) antigen, and on ppd 40 the DHR to HEWL was assessed using the aforementioned protocol. Analysis of ewe sera showed a positive correlation between organic Se supplementation and higher Se levels (P < 0.01). Moreover, statistical analyses of the DHR results using a generalized least squares linear model (RStudio) indicate that Se supplementation increased the immune response compared to the non-supplemented ewes (P < 0.01). However, no significant differences between organic and inorganic Se supplementation were found. In lambs, higher ewe Se supplementation resulted in higher Se muscle content (P >0.01). and organic Se supplementation to ewes significantly increased lamb Se muscle content compared to inorganic Se supplementation (P >0.01). Finally, analyses of the lamb DHR showed that maternal organic Se supplementation improved the lamb immune response compared to the control group (P >0.05). Therefore, organic Se supplementation optimally enhances ewe and lamb Se status and their adaptive immune response compared to the inorganic and control groups. This knowledge will guide optimal ewe Se-supplementation choices during pregnancy and postpartum, thus promoting lamb and ewe health.