Supranutritional selenium increases mammary gland vascularity in postpartum ewe lambs

Objectives were to determine the effects of maternal dietary supranutritional Se and nutritional plane during gestation on capillary surface density, capillary area density, and angiogenic factor expression in the developing mammary gland of primiparous ewes. Selenium treatments were initiated at breeding [adequate Se (ASe; 9.5 μg/kg of body weight) vs. high Se (HSe; 81.8 μg/kg of body weight)] and nutritional planes at d 50 of gestation [Low, 60%; moderate (Mod), 100%; and High, 140% of requirements). Mammary glands were collected within 24h postpartum. Vascular development was assessed in the glandular portion of the mammary gland. Vascularity was determined for mammary tissue with the following measurements taken: the cross-sectional capillary area density (total capillary area as a proportion of tissue area) and capillary surface density (CSD; total capillary circumference per unit of tissue area). High-Se ewes had greater capillary surface and area densities compared with ASe ewes. A tendency existed for an Se × plane of nutrition interaction for CSD with maternal diet not affecting CSD in HSe ewes, but Low ewes had a decreased CSD compared with Mod ewes, with High being intermediate in ASe ewes. Moreover, HSe-Low and HSe-High ewes had increased CSD compared with ASe-Low and ASe-High, respectively. Although Se status did not influence angiogenic factor mRNA expression, mammary glands from Low ewes tended to have increased VEGF and FLT1 mRNA expression compared with High ewes, with Mod being intermediate. Maternal plane of nutrition did not affect mammary gland glutathione peroxidase activity, but it was increased in HSe compared with ASe ewes. Increased mammary capillary nutrient exchange area may contribute to previously observed changes in colostrum quality.