Original ResearchThe Effects of Selenium Source on Measures of Selenium Status of Mares and Selenium Status and Immune Function of Their Foals
Introduction
The effect of the maternal selenium (Se) intake on the Se status of offspring has received considerable attention in humans and domestic animal species [1], but little information is currently available for horses. In domestic livestock, both transplacental Se transfer as well as transfer through colostrum and milk can influence the Se status of the fetus and neonate [2], [3]. Colostrum and milk Se concentrations depend on both the amount and source of Se (inorganic vs. organic) available in the maternal diet; organic Se supplementation in cows has led to higher Se concentration in milk compared with inorganic Se [2], [3], [4], [5], [6], [7]. Similarly, colostrum and milk Se concentrations after foaling were higher in mares receiving organic Se compared with those receiving inorganic Se [8] or no Se [7], and foals born to mares receiving organic Se had higher serum Se concentrations at birth.
Se intake and metabolism have been linked to immune function in various species, leading to increased interest in the relationship between maternal and neonatal Se status, and neonatal immune function [8], [9], [10], [11], [12]. Previously, we have shown that dietary Se, both concentration and source, influences immune function in adult horses, and that these effects may be mediated in part by alterations in relative cytokine expression of neutrophils and lymphocytes [13]. These results support and extend the results of previous research showing that Se status affects both innate and adaptive immunity, including neutrophil and macrophage function, lymphocyte function, and antibody production in humans and animals [14], [15], [16], [17], [18], [19].
The equine neonate is at high risk of infectious disease and sepsis [20]. For this reason, studies examining the effect of Se supplementation and source on specific immune responses of equine neonates should be of particular interest; however, there is a dearth of published research on this species. A study in rats found that thymocytes from neonates receiving low-Se milk exhibited impaired activation in vitro. Further, the percentages of CD8 cytotoxic T-lymphocytes, CD2 T-lymphocytes, B-lymphocytes, and natural killer cells were decreased in the spleen of neonates nursed by mothers receiving a low-Se diet [11]. A study of Se supplementation and immune function in foals found greater antibody titers to influenza virus in foals born to mares supplemented with 3 mg of Se per day compared with mares receiving 1 mg of Se per day [8]. Supplementation of mares with either an inorganic or organic Se at a rate of 3 mg of Se per day was associated with higher concentration of serum IgG in foals at 2 weeks of age compared with foals born to the mares receiving a daily amount of 1 mg of Se [21]. A more recent study found no effect of Se fed to mares (as Se yeast, 0.3 mg/kg dry matter [DM]) on foal serum IgG measured in 1-day-old foals [22]. The effects of Se supplementation on the cellular determinants of the equine immune response have not been studied to date.
The purpose of this study was to investigate the effect of dietary Se source on the Se status of mares and, consequently, the Se status and immune function of their foals. Measurements of interest included the effect of Se source on colostrum and milk Se concentrations as well as plasma and red blood cell Se concentrations of mares and foals. Furthermore, measures of innate and adaptive immune function of foals were studied, including lymphocyte proliferation in response to the mitogen concanavalin A (ConA) and relative cytokine gene expression of lymphocytes and neutrophils.
Section snippets
Experimental Animals and Study Design
Twenty multiparous Standardbred mares due to foal between April and June 2008, from 3 farms on Prince Edward Island, were included in the study following owner’s consent.
The experimental animals were kept on their home farm for the duration of the study. Nutritional management before the beginning of the feeding trial was reflective of the practices of each of the co-operating farms. Each mare was started on its assigned experimental ration 2 months before its estimated due date (based on a
Results
Each mare produced a live foal following a normal gestation and foaling. Follow-up to 1 day of age was possible for 18 foals (nine from each group), and to 30 days of age for 16 foals (eight from each group). Foals were lost to follow-up for the following reasons: one foal died shortly after birth (presumed septicemia; organic group); one foal was sick at birth and was consequently hospitalized (presumed septicemia; inorganic); one foal was diagnosed with failure of passive transfer of immunity
Discussion
The form of Se fed to mares during late pregnancy and early lactation influenced red blood cell Se concentration in 1-month-old foals, and influenced measures of foal immune response, specifically the relative gene expression of IL-2, TNFα, and IFNγ in lymphocytes.
Recently, there has been increased interest in the effect of Se source on the Se status of mares and their foals [7], [8], [22]. Janicki et al. [8] showed that serum Se concentrations were greater in mares receiving organic Se when
Conclusion
Whether mares were supplemented with organic or inorganic Se during late pregnancy and lactation affected foal Se status and relative gene expression of certain lymphocyte cytokines, namely, IL-2, TNFα, and IFNγ. These findings warrant further investigation of the effect of Se nutrition and foal immunity. Furthermore, the results from this study suggest that pregnant mares should receive Se supplementation for more than 2 months before foaling and may require higher concentrations of
Acknowledgments
The authors express their sincerest thanks to Dr. Amanda Adams for her help with the gene expression. Furthermore, the authors also acknowledge Judy Sheppard for her help with the lymphocyte blastogenesis and Alejandra Betancourt for her help with the PCR analysis.
This study was funded by the Sir James Dunn Animal Welfare Centre.
References (44)
- et al.
Selenoproteins and maternal nutrition
Comp Biochem Physiol B Biochem Mol Biol
(2008) - et al.
Effect of selenium supplementation of cows on maternal transfer of selenium to fetal and newborn calves
J Dairy Sci
(1995) - et al.
Effects of prenatal source and level of dietary selenium on passive immunity and thermometabolism of newborn lambs
Small Rumin Res
(2001) - et al.
Effects of selenium and vitamin E on the immune responses of domestic animals
Res Vet Sci
(1996) - et al.
Selenium in the immune system
J Nutr
(2003) Equine neonatal sepsis
Vet Clin North Am Equine Pract
(2005)- et al.
Glutathione peroxidase activity in bovine serum and erythrocytes in relation to selenium concentrations of blood, serum and liver
Res Vet Sci
(1980) Semi-automated fluorimetric determination of nanogram quantities of selenium in biological material
Anal Chim Acta
(1979)- et al.
Foals are interferon gamma-deficient at birth
Vet Immunol Immunopathol
(2006) - et al.
Advanced age in horses affects divisional history of T cells and inflammatory cytokine production
Mech Ageing Dev
(2008)