Organic and inorganic selenium: III. Ewe and progeny performance

Abstract

Selenium is an essential micronutrient in sheep, and deficiency can limit lamb growth and survival. To evaluate how different chemical forms of Se administered to mature ewes at comparative dosages affect ewe and progeny performance, 240 ewes were divided into 8 treatment groups (n = 30 each) and drenched weekly with no Se; at the maximum FDA-allowed concentration with inorganic Na-selenite or organic Se-yeast (4.9 mg Se/wk); with inorganic Na-selenate (8.95 mg Se/wk); or with inorganic Na-selenite and organic Se-yeast at supranutritional concentrations (14.7 and 24.5 mg Se/wk, respectively). The treatment period started approximately 2 wk before breeding and lasted for 62.5 wk. Ewes of the no-Se and Se-yeast groups continued treatments for another 21 to 24 wk through a second lambing season. Chemical form or dosage of Se did not affect ewe reproductive performance based on proportion of ewes lambing in each treatment group, or number of lambs born, nursed, or weaned per ewe (all P > 0.10). Ewes receiving the highest supplementation rate of Se-yeast at 24.5 mg Se/wk had higher BCS (scale 1 to 5) at the end of yr 1 (2.95 vs. 2.66; P = 0.05) than ewes receiving Se-yeast at 4.9 mg Se/wk. Performance was better in lambs from ewes receiving Se-yeast at 24.5 mg Se/wk than in lambs from ewes receiving Se-yeast at 4.9 mg Se/wk or no Se. In yr 1, lambs from ewes receiving Se-yeast at 24.5 vs. 4.9 mg Se/wk were heavier at 120 d of age (37.0 vs. 34.2 kg; P = 0.05). In yr 2, lambs from ewes receiving Se-yeast at 24.5 mg Se/wk were or tended to be heavier at 60 d of age than lambs from ewes receiving no Se (21.2 vs. 19.0 kg; P = 0.04) or lambs from ewes receiving Se-yeast at 4.9 mg Se/wk (19.2 kg; P = 0.09). This effect was more pronounced in ewes raising multiple lambs. We conclude that supranutritional supplementation of ewes with Se-yeast at 24.5 mg Se/wk improves lamb growth and ewe health without negatively affecting reproductive performance.

Effect of Selenium Yeast Supplementation on Naturally Acquired Parasitic Infection in Ewes

“…We also observed differences in body condition scores of study ewes at week 60, as we have reported previously in a companion paper [27]. Therefore, we started to measure fecal egg counts in week 63.…”

“…None of the ewes receiving supranutritional Se-yeast supplements, nor their progeny, showed adverse clinical signs at any time throughout two lambing seasons. To the contrary, the progeny gained more weight in both lambing seasons and had better survival rates until weaning in the second lambing season [27]. Benefits of supranutritional Se-yeast supplementation in ewes included more rapid recovery of foot rot lesions [29], improved immune function (increased Escherichia coli killing by neutrophils, increased antibody titers to the novel antigen keyhole limpet hemocyanin, and increased neutrophil expression of genes involved in bacterial pathogen recognition and response) [30,31], and increased immunoglobulin G transfer to their offspring [32].…”

“…We are interested in supranutritional Se supplementation (dosages greater than that required for optimal expression of selenoproteins, but less than maximal tolerable levels) to improve health and performance in ruminant livestock. We showed in a companion paper that supplementing Se-replete ewes for 85 weeks with 24.5 mg Se/week as Se yeast improved body condition scores of ewes at 60 weeks [27]. This was 5× the FDA upper limit for supplementing ruminant diets, but less than the 5 mg/kg diet, which is considered to be the maximal tolerable level for ruminants [28].…”

The effect of organic selenium in feeding of ewes in late pregnancy on selenium transfer to progeny

“…Nutrient transfer from dam to offspring occurs via two pathways: placental transfer and colostrum/milk ingestion (Hefnawy et al, 2014). Selenium placental transfer was demonstrated by De Toledo and Perry (1985) and Stewart et al (2012) and fetal selenium concentrations have been shown to be greater (Stewart et al, 2012) than corresponding maternal selenium concentrations. Addition of Se to the maternal diet increased Se concentration in both serum and colostrum (Phipps et al, 2008;Slavik et al, 2008;Karren et al, 2010;Kachuca et al, 2013).…”

“…Provision of Se to the mother during pregnancy is an effective method to meet Se requirements in the newborn, R. Bras. Zootec., 46(2): [147][148][149][150][151][152][153][154][155]2017 as it efficiently passes through the placental barrier into fetal tissues and is also transferred into colostrum and milk (Rock et al, 2001;Stewart et al, 2012). A close relationship has been detected between offspring serum Se and maternal levels after feeding with Se, once the offspring obtains this nutrient via the placenta before birth (Hefnawy et al, 2014).…”