|Taylor, Joshua - Bret|
Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/24/2008
Publication Date: 4/16/2009
Citation: Taylor, J.B., Reynolds, L.P., Redmer, D.A., Caton, J.S. 2009. Maternal and fetal tissue selenium loads in nulliparous ewes fed supranutritional and excessive selenium during mid to late pregnancy.. Journal of Animal Science. 87:1828-1834. Interpretive Summary: In pregnant ewe lambs, supranutritional selenium from selenium-enriched wheat grain 1) resulted greater maternal and fetal tissue and plasma selenium loads, 2) seemed to cross the placenta to the fetus at greater efficiency than sodium selenite, and 3) was equivalent in selenium -loading potential to sodium selenate-selenium that was fed at 5-times the amount of wheat grain-selenium. Sodium selenate fed at 345 mcg of selenium/kg of body weight and selenium-enriched wheat grain at 70 mcg of selenium/kg of body weight to pregnant ewe lambs neither induced signs of selenosis nor negatively influence ewe lamb or fetal growth and development. Based on the sodium selenate data, these ewes in this study were capable of consuming greater than twice the current selenium maximum tolerance level. Finally, a natural selenium-enriched feedstuff was effective at simultaneously enriching maternal and fetal muscle. Such enrichment could enable producers to 1) graze ewes and offspring on selenium-deficient ranges for extended periods without the need of selenium supplementation, and 2) have available for market a selenium-enriched meat product.
Technical Abstract: The objectives were to describe the effects of Se on fetal and maternal Se load when fed supranutritionally as Se-enriched wheat grain, and supranutritionally and excessively as sodium selenate to nulliparous pregnant ewes during pregnancy. Pregnant, whitefaced-cross, nulliparous ewes (n = 32; 45.6 ± 2.3 kg; 330 ± 17 d of age) were randomly assigned to treatment diets. The treatments were: 3.5 mcg Se•kg BW-1 d-1, with Se from the inherent Se in the diet (C1X); 70 mcg Se/kg BW-1 d-1, with Se from supplemental sodium selenate (S20X); 345 mcg Se/kg BW-1 d-1, with Se from supplemental sodium selenate (S100X); and 70 mcg Se/kg BW-1 d-1, with Se from naturally-occurring Se-enriched wheat grain (W20X). Treatment diets were initiated 50 d, and continued until slaughter at 134 d, after breeding. Plasma samples were collected from ewes on d 50, 64, 78, 92, 106, 120, and 134 and from fetuses on d 134 of pregnancy. Ewes were randomly assigned to 1 of 8 consecutive slaughter days at d 134 ± 4 d. Maternal and fetal longissimus muscle, kidney, and liver samples were collected and stored. Tissue and plasma samples were analyzed for Se. Compared with other treatments, S100X resulted in the greatest maternal tissue and plasma Se loads (P < 0.001). However, based on the total amount of Se consumed during the treatment period, efficiency of Se loading was greatest for the W20X treatment. Compared with C1X and S20X, Se loading in fetal tissues and plasma was greater (P < 0.01) for S100X and W20X treatments. In S100X treated ewes, maternal plasma Se increased rapidly from d 50 to 64 but remained unchanged thereafter. Maternal plasma Se increased steadily throughout the experiment in W20X and S20X ewes, but remained unchanged in C1X throughout the study. Sodium selenate fed at 345 mcg Se/kg BW-1 d-1 and Se-enriched wheat grain at 70 mcg Se/kg BW-1 d-1 to nulliparous pregnant ewe lambs neither induced sings of selenosis nor negatively influenced ewe lamb or fetal growth and development. Therefore, ewes in this study were capable of consuming greater than twice the current Se maximum tolerable limit as sodium selenate without experiencing selenosis. Selenium from Se-enriched wheat grain treatment seemed to cross the placenta to the fetus at greater efficiency than did Se from sodium selenate, and was equivalent in Se-loading potential to sodium selenate-Se that was fed at 5-times the amount of wheat grain-Se.