|Taylor, Joshua - Bret|
Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/13/2010
Publication Date: 1/1/2011
Publication URL: jas.fass.org/content/89/1/59
Citation: Lekatz, L.A., Caton, J.S., Taylor, J.B., Reynolds, L.P., Redmer, D.A., Vonnahme, K.A. 2011. Maternal selenium supplementation and timing of nutrient restriction in pregnant sheep: Impacts on nutrient availability to the fetus. Journal of Animal Science. 89:59-76. Interpretive Summary: Marginal selenium deficiency can result in a 33% loss in annual revenue from a ewe flock. Frequent supplementation of selenium is necessary for sheep produced in selenium-deficient regions. Unfortunately, the extensiveness and ruggedness of Intermountain West rangelands often prohibits frequent access to grazing sheep. Therefore, a low-frequency supplement strategy is needed that enhances long-term selenium status of grazing sheep. Through use of selenomethionine-rich feed sources, we have developed such a strategy. However, the strategy requires that selenium must be fed at 10- to 20-fold the daily requirement. Because of inaccurate generalizations about selenium toxicity (e.g., NRC, Nutrient Requirements of Sheep, 1985), many are concerned that providing selenium at this level of intake may be unsafe for livestock. Therefore, we report on the effects of feeding selenium, from selenomethionine-rich sources, at 10-fold the daily requirement to ewes during that last 90 days of pregnancy. Selenium fed to pregnant ewes at 10-fold the daily requirement decreased serum amino acids, specifically methionine, histidine, and phenylalanine. However, no general symptoms of selenium toxicity were observed in the pregnant ewe or fetus. We conclude that it is safe to feed pregnant ewes selenium, from selenomethionine-rich feeds, up to 10-fold the daily requirement.
Technical Abstract: To determine the effects of maternal Se intake and plane of nutrition during mid and/or late gestation on AA concentrations and metabolite levels in the dam and fetus, pregnant ewe lambs (n = 64) were assigned to 1 of 8 treatments arranged in a 2 × 2 × 2 factorial array: Se level [initiated at breeding; adequate (ASe; 3.05 ug/kg BW) or high (HSe; 70.4 ug/kg BW)] and nutritional level [100% (control; CON) or 60% (restricted; RES) of NRC recommendations] fed at different times of gestation [d 50 to 90 (Mid) or d 91 to 132 (Late)]. A blood sample was obtained from each ewe and fetus on d 132 of gestation and used to measure circulating levels of glucose, NEFA, BUN, and AA. The late RES ewes and their fetuses had less (P < 0.03) circulating glucose compared with late CON ewes and fetuses at d 132; however, no effect (P > 0.14) of diet on the fetal:maternal glucose concentration ratio was observed. Late RES ewes had a lower (P = 0.01) fetal:maternal NEFA ratio compared with late CON ewes. Ewes fed ASe had a greater (P = 0.01) fetal:maternal BUN ratio compared to HSe ewes. Fetal:maternal ratios of total circulating AA, total essential AA, and total non-essential AA were each affected (P < 0.03) by the combination of Se treatment and late gestation nutritional level.