ARS | Publication request: Nutritional plane and selenium supply during gestation impact yield and nutrient composition of colostrum and milk in primiparous ewes

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 30, 2011
Publication Date: May 1, 2011
Citation: Meyer, A.M., Reed, J.J., Neville, T.L., Maddock-Carlin, K.R., Thorson, K.A., Taylor, J.B., Reynold, L.P., Luther, J.D., Redman, J.S., Vonnahme, K.A., Caton, J.S. 2011. Nutritional plane and selenium supply during gestation impact yield and nutrient composition of colostrum and milk in primiparous ewes. Journal of Animal Science. 89:1627-1639.

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 a selenium-rich wheat milling coproducts, a selenomethionine-rich feed source, we have developed such a strategy using. 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, as a selenium-rich wheat milling coproduct, at 20-fold the daily requirement to ewes during that last 90 days of pregnancy. Selenium fed at 20-fold the daily requirement resulted in greater colostrum and milk yield, and greater amounts of selenium in the milk. Overall, no general symptoms of selenium toxicity were observed. We conclude that it is safe to feed pregnant ewes selenium, from selenomethionine-rich feeds, up to 20-fold the daily requirement.

Technical Abstract: Objectives were to investigate effects of nutritional plane and Se supply during gestation on yield and nutrient composition of colostrum and milk in first parity ewes. Rambouillet ewe lambs (n = 84, age = 240 +/- 17 d, BW = 52.1 +/- 6.2 kg), were allocated to 6 treatments in a 2 x 3 factorial array. Factors included Se [adequate Se (ASe, 11.5 ug/kg BW) or high Se (HSe, 77.0 ug/kg BW)] initiated at breeding and nutritional plane [60% (RES), 100% (CON), or 140% (HIH) of requirements] initiated at d 40 of gestation. Ewes were fed individually from d 40 and lambs were removed at parturition. Colostrum was milked from all ewes at 3 h postpartum, and half of the ewes (n = 42) were transitioned to a common diet meeting lactation requirements and mechanically milked for 20 d. Colostrum yield was greater (P = 0.02) for HSe ewes than ASe, whereas CON had greater (P < 0.05) colostrum yield than RES and HIH. Colostrum Se (%) was greater (P < 0.01) for HSe than ASe. Ewes fed HSe had less colostrum butterfat (%) but greater (P < 0.05) total butterfat, solids-not-fat, lactose, protein, milk urea N, and Se than ASe. Colostrum from HIH ewes had greater (P < 0.02) solids-not-fat (%) than RES, whereas RES had greater (P < 0.04) butterfat (%) than CON and HIH. Ewes fed the CON diet had greater (P = 0.01) total colostrum butterfat than HIH. Total solids-not-fat, lactose, and protein were greater (P < 0.05) in colostrum from CON than RES and HIH. Ewes fed HSe had greater (P < 0.01) milk yield (g/d and mL/d) than ASe, and CON and HIH had greater (P < 0.01) yield than RES. Milk protein (%) was greater (P = 0.01) in RES compared with CON or HIH. Ewes fed HSe had greater (P < 0.01) milk Se (µg/g and mg/d) than ASe on each sampling day. Milk from CON and HIH ewes had greater (P < 0.01) total solids-not-fat, lactose, protein, and milk urea N than RES. Total Se was greater (P = 0.02) in milk from ewes fed the CON diet compared with RES. Somatic cell count and total somatic cells were greater (P < 0.05) in milk from CON than RES. A cubic effect of day (P < 0.01) was observed for milk yield (g and mL). Butterfat, solids-not-fat, lactose, milk urea N, and Se concentration responded quadratically (P < 0.01) to day. Protein (%), total butterfat, and total Se, and somatic cells (cells/mL and cells/d) decreased linearly (P < 0.01) with day. Results indicate that gestational nutrition affects colostrum and milk yield and nutrient content, even when lactational nutrient requirements are met.