|Taylor, Joshua - Bret|
Submitted to: Animal Reproduction Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2009
Publication Date: 7/1/2009
Publication URL: http://doi:10.1016/j.anirepro.2009.05.009
Citation: Lekatz, L.A., Ward, M.A., Borowicz, P.P., Taylor, J.B., Redmer, D.A., Grazul-Bilska, A.T., Reynolds, L.P., Caton, J.S., Vonnahme, K.A. 2009. Cotyledonary responses to maternal selenium and dietary restriction may influence alteration in fetal weight and fetal liver glycogen sheep. Animal Reproduction Science. 117:216-225. Interpretive Summary: Some rangelands of the Intermountain West are deficient in the mineral selenium. Forage growth may be stalled during drought, which may limit the total nutrition available for grazing, pregnant sheep. Providing supplemental nutrition to sheep that are grazing extensive rangelands is often prohibitive or very costly. Scientists at the USDA, ARS, U. S. Sheep Experiment Station, Dubois, ID, and North Dakota State University, Fargo, have considered extensively these production challenges. They have studied how limited nutrition and high levels of dietary selenium during pregnancy affected growth of adolescent ewes and their fetuses. The results show that the fetus and placenta adapt to nutrient restriction during mid- to late pregnancy and ensure fetal survival. Furthermore, feeding diets rich in organically-bound selenium during mid- to late pregnancy “loads” the ewe and fetus with selenium, and this will enable the ewe and lambs to graze selenium deficient ranges without the need for supplemental selenium.
Technical Abstract: To examine the effects of maternal supranutritional Se and nutrient restriction during mid and late gestation on placental characteristics and fetal liver glycogen, ewes received either adequate Se (ASe) or high Se (HSe) prior to breeding. On day 64 of gestation, ASe and HSe ewes remained at 100% of requirements (controls; CON) or were restricted (RES; 60% of requirements). On day 135 of gestation, fetal weight (P less than/equal to 0.08) was greatest in both HSe and CON ewes. Placentome number, mass, and caruncular and cotyledonary weight were not different (P greater than/equal to 0.17) among treatments. Fetal mass:placental mass ratio was less (P = 0.06) in RES compared to CON ewes. Compared to ASe, HSe exhibited increased (P less than/equal to 0.08) cellular proliferation and DNA concentration and decreased (P = 0.07) cellular size in cotyledonary tissue. Nutritional restriction decreased (P less than/equal to 0.08) cotyledonary protein concentration and cellular size. Expression of VEFG receptor 1 (Flt) mRNA in cotyledonary tissue was greater in HSe vs. ASe ewes (P = 0.06) and in RES vs. CON ewes (P = 0.08). There was no effect of diet on caruncular growth parameters (P greater than/equal to 0.13) or on placental vascularity (P greater than/equal to 0.11). Progesterone was greater (P less than/equal to 0.08) in ASe-RES ewes compared to all groups at day 90 and ASe-CON and HSe-CON at day 104. Although fetal glucose and cortisol concentrations were not affected by diet, fetal liver glycogen was greater (P = 0.04) in ASe-RES compared to ASe-CON and HSe-RES ewes. Both Se and nutritional plane may impact placental function and fetal growth, as fetal weight and liver glycogen are altered despite similar placental vascularity measurements.