Maternal dietary intake alters organ mass and endocrine and metabolic profiles in pregnant ewe lambs.

To determine the impacts of Se supply and maternal dietary intake on ewe organ mass and endocrine and metabolic changes throughout gestation, pregnant first parity ewes (n=77) were allocated to 6 treatments in a 2×3 factorial array. Factors included Se [adequate Se (ASe; 9.5μg/kg BW) vs. high Se (HSe; 81.8μg/kg BW)] initiated at breeding and dietary intake [60% (RES), 100% (CON), or 140% (EXC) of requirements] initiated on d 50 of gestation. Ewes were individually fed and blood samples from the jugular vein were obtained approximately every 14 d from d 50 until parturition. Maternal Se supply did not impact endocrine or metabolic status. There was a nutritional intake by day interaction for NEFA, blood urea nitrogen (BUN), insulin, triiodothyronine (T3), thyroxine (T4), progesterone (P4), and estradiol-17β (E2). As expected, with increased maternal intake, NEFA concentrations were reduced. During the last weeks of gestation, BUN and insulin were elevated in EXC compared with RES ewes. Although the pattern of T3 and T4 differed throughout gestation within a treatment group, as maternal intake increased, circulating T3 and T4 were increased. For P4 and E2, as maternal dietary intake increased, there was a reduction in the steroid concentrations in jugular blood. There was only a main effect of maternal nutrition (P<0.001) for cortisol concentrations with EXC ewes having greater concentrations than RES and CON ewes, which did not differ. Although Se is known to influence thyroid hormone metabolism, supranutritional levels during pregnancy did not alter circulating T3 and T4 concentrations. Alterations in maternal endocrine status may have influenced placental transport of nutrients to the developing fetus, which we have shown previously is affected by maternal dietary Se and intake. In addition, the alterations in mammary gland weight that we observed may explain the impact of maternal nutrition on mammary gland function and colostrum production, thereby further impairing growth of developing neonates.