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This Article Full Text Full Text (PDF) All Versions of this Article: jas.2007-0509v1 86/5/1254    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Ward, M. A. Articles by Caton, J. S. PubMed PubMed Citation Articles by Ward, M. A. Articles by Caton, J. S.

Effects of selenium supply and dietary restriction on maternal and fetal metabolic hormones in pregnant ewe lambs¹

M. A. Ward^*,2, T. L. Neville^*, J. J. Reed^*, J. B. Taylor, D. M. Hallford, S. A. Soto-Navarro, K. A. Vonnahme^*, D. A. Redmer^*, L. P. Reynolds^* and J. S. Caton^*,3

^* Center for Nutrition and Pregnancy and Animal and Range Sciences Department, North Dakota State University, Fargo 58105; and USDA-ARS, US Sheep Experiment Station, Dubois, ID 83423; and and Animal and Range Sciences Department, New Mexico State University, Las Cruces 88003

³ Corresponding author: Joel.Caton{at}ndsu.edu

The objective of these studies was to evaluate the effects of dietary restriction and Se on maternal and fetal metabolic hormones. In Exp. 1, pregnant ewe lambs (n = 32; BW = 45.6 ± 2.3 kg) were allotted randomly to 1 of 4 treatments. Diets contained (DM basis) either no added Se (control), or supranutritional Se added as high-Se wheat at 3.0 mg/kg (Se-wheat), or sodium selenate at 3 (Se3) and 15 (Se15) mg/kg of Se. Diets (DM basis) were similar in CP (15.5%) and ME (2.68 Mcal/kg). Treatments were initiated at 50 ± 5 d of gestation. The control, Se-wheat, Se3, and Se15 treatments provided 2.5, 75, 75, and 375 µg/kg of BW of Se, respectively. Ewe jugular blood samples were collected at 50, 64, 78, 92, 106, 120, and 134 d of gestation. Fetal serum samples were collected at necropsy on d 134. In Exp. 2, pregnant ewe lambs (n = 36; BW 53.8 ± 1.3 kg) were allotted randomly to treatments in a 2 x 2 factorial arrangement. Factors were nutrition (control, 100% of requirements vs. restricted nutrition, 60% of control) and dietary Se (adequate Se, 6 µg/kg of BW vs. high Se, 80 µg/kg of BW). Selenium treatments were initiated 21 d before breeding, and nutritional treatments were initiated on d 64 of gestation. Diets were 16% CP and 2.12 Mcal/kg of ME (DM basis). Blood samples were collected from the ewes at 62, 76, 90, 104, 118, 132, and 135 d of gestation. Fetal blood was collected at necropsy on d 135. In Exp.1, dietary Se source and concentration had no effect (P > 0.17) on maternal and fetal serum IGF-I, triiodothyronine (T₃), or thyroxine (T₄) concentrations. Selenium supplementation increased (P = 0.06) the T₄:T₃ ratio vs. controls. In Exp. 2, dietary Se had no impact (P > 0.33) on main effect means for maternal and fetal serum IGF-I, T₃, or T₄ concentrations from d 62 to 132; however, at d 135, high-Se ewes had lower (P = 0.01) serum T₄ concentrations than adequate-Se ewes. A nutrition by Se interaction (P = 0.06) was detected for the T₄:T₃ ratios; ewes fed restricted and adequate-Se diets had greater (P = 0.10) T₄:T₃ ratios compared with the other treatments. Nutrient-restricted ewes had lower (P < 0.05) serum IGF-I, T₃, and T₄ concentrations. Fetal serum IGF-I concentrations were lower (P = 0.01) in restricted-vs. control-fed ewes; however, fetal T₃ and T₄ concentrations were unaffected (P > 0.13) by dietary Se or maternal plane of nutrition. These data indicate that dietary Se may alter maternal T₄:T₃ ratios. In addition, nutrient restriction during gestation reduces maternal IGF-I, T₃, and T₄ and fetal IGF-I concentrations.

Key Words: ewe • fetus • metabolic hormone • pregnancy • selenium