|Taylor, Joshua - Bret|
Submitted to: Western Section of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/15/2004
Publication Date: 5/1/2004
Citation: Ward, M.A., Caton, J.S., Taylor, J.B., Lawler, T.L., Hallford, D.M., Redmer, D.A., Reynolds, L.P. 2004. Effect of level and source of selenium on maternal and fetal metabolic hormones in pregnant yearling ewes. Proceedings of 55th Western Section of the American Society of Animal Science. p. 367. Interpretive Summary: The objective of this study was to determine how source and level of selenium influence maternal and fetal serum levels of IGF-1, T3, T4, and Se. Thirty two pregnant Targhee ewe lambs were used. Neither source nor level of Se affected maternal IGF-1, T3, or T4. Serum Se concentrations in the ewe and fetus increased due to source and level of dietary Se. Fetal serum Se is responsive to maternal dietary Se source.
Technical Abstract: To examine effects of source (organic vs. inorganic) and level (0.1, 3, and 15 ppm) of dietary Se on maternal and fetal insulin like growth factor-1 (IGF-1), and thyroid hormones (T3 and T4), 32 pregnant Targhee ewe lambs (45.6 ± 10.5 kg, 330 ± 30 d of age) were randomly allotted to one of four treatments in a completely randomized design. Treatments were: control (CON; 0.1 ppm Se), Se-wheat (SW; 3 ppm Se), 3 ppm selenate (S3), and 15 ppm selenate (S15). The SW diet was formulated using 32% high Se wheat. Diets were similar in CP (15.5%) and energy (2.68 Mcal of ME), and fed to meet or exceed requirements. Diets were initiated at 50 + 5 d of gestation. The SW and S3 diets (supranutritional Se levels) provided 75 mg/kg BW of Se, while the S15 treatment provided 375 mg/kg BW of Se. Jugular blood samples were taken from ewes at 50, 64, 78, 92, 106, 120, and 134 d of gestation. Fetal blood samples were taken at d 134 (slaughter). Maternal IGF-1, T3, and T4 were not affected (P > 0.1) by treatment, but were altered (P < 0.05) by stage of gestation. Maternal IGF-1 increased as gestation progressed, whereas T3 decreased, and T4 remained unchanged. In the fetus, correlations were observed between fetal BW and serum IGF-1. In CON and SW fed ewes, r values were 0.53 and 0.66, respectively. Conversely this correlation did not exist in ewes fed 3 ppm or 15 ppm as selenate. The S15 treated ewes had the greatest (P < 0.001) plasma Se levels (1.3 ppm), the S3 and SW had similar plasma Se levels and CON had the lowest plasma Se concentration. Fetal serum selenium concentrations for SW and S15 treatments were greater (P < 0.001) than S3 and CON (0.327 and 0.366, vs. 0.177 and 0.114 ± 0.015 ppm, respectively). Selenium source may influence fetal IGF, but has little impact on T3 and T4. Fetal plasma was higher in Se when the dietary source was high Se wheat compared with Se salt.