195 Maternal selenium supplementation supports lamb selenium status without affecting immune function.

Abstract Selenium (Se) is an essential trace mineral vital to ruminant health and productivity. Se deficiencies in sheep can lead to reduced immune function in ewes and their resulting lambs. While inorganic Se supplementation is less costly, organic Se supplementation offers more bioavailable Se, and may be a more proficient method of ensuring lambs receive enough Se from their ewes. The objective of this study was to assess the impact of maternal organic and inorganic Se supplementation on offspring health throughout development by assessing lamb growth, antigen-specific acquired immune responses, and the acute-phase response to lipopolysaccharide (LPS) immune challenge. In a randomized complete block study design, Dorset-Rideau ewes (n=110) were enrolled in a feeding trial starting on gestation day (gd) 110 and ending on postpartum day (ppd) 52. All ewes were fed a Se-deficient diet and supplemented with either no Se, 0.3 mg/day inorganic Se (sodium selenite), 0.3 or 0.6 mg/day organic Se (hydroxy-selenomethionine) via oral gavage. The offspring received no Se until ppd 10, other than what was provided via maternal nursing, at which time creep feed containing both inorganic and organic Se was introduced. Serum was collected from lambs on ppds 0, 2, 10 and 52 to assess Se transfer from ewe to lamb, and muscle samples were collected on ppd 10 to assess Se stores in lambs. Ewes were intramuscularly (i.m.) injected with 0.5 mg OVA antigen on gds 110 and 120, and lamb serum was subsequently collected on ppds 0 and 2 to assess maternal transfer of anti-OVA antibodies. Lambs were also injected i.m. with 0.5 mg hen egg white lysozyme (HEWL) antigen on ppds 20 and 30, and on ppd 40, the dermal hypersensitivity response (DHR) to HEWL was assessed by measuring change in skin-fold thickness over time after intradermal HEWL injection. Serum was also collected on ppds 20, 30 and 40 to investigate differences in serum anti-HEWL antibody concentrations among treatments. On ppd 52, 2 days post-weaning, lambs were administered 400 ng/kg LPS intravenously (i.v.) and serum was obtained at 0 and 4 hours post LPS-injection to examine acute-phase cytokine and cortisol responses. Rectal temperatures were also recorded hourly. Lambs from ewes in both organic Se treatments had higher serum Se levels on ppd 0, 2 and 10 as compared to lambs from ewes from the inorganic Se and Se deficient treatments (P<0.01). Muscle analyses also showed these lambs had higher Se stores (P<0.0001). Serum anti-OVA and anti-HEWL antibody concentrations did not differ among treatment groups; however, skinfold thickness was significantly reduced at 48 hours post-injection as compared to 6 hours post-injection in lambs whose ewes were supplemented with 0.6 mg organic Se (P<0.01). Finally, although all animals responded to LPS challenge, there were no significant differences in rectal temperatures, cortisol or cytokine responses among the Se treatments.