Effects of prenatal source and level of dietary selenium on passive immunity and thermometabolism of newborn lambs.

The objective of this study was to determine the effects of the amount and chemical form of Se fed to pregnant ewes on concentrations of thyroid hormones, Se in tissues, immunoglobulins (Ig) in serum, and measures of thermometabolism in ewes and their newborn lambs. Pregnant ewes (n=21) were randomly assigned to receive a diet deficient of Se (<0.02ppm) or supplemented to provide 0.3ppm Se from either sodium selenite or selenized yeast (SeY). Pregnant ewes which were fed additional Se had increased (P<0.05) concentrations of Se in whole blood and serum, greater activity of glutathione peroxidase (GSHpx), and higher concentrations of tri-iodothyronine (T(3)) and thyroxine (T(4)). At 12h of age, lambs of ewes given Se had higher (P<0.05) concentrations of Se in blood and liver, greater activities of GSHpx, and tended (P<0.1) to have higher T(3) levels. When the two Se supplements were compared, lambs of ewes which were fed with SeY had higher (P<0.001) concentrations of Se and activities of GSHpx (P<0.05) in blood than lambs of ewes fed with selenite. Concentrations of Se in colostrum were increased (P<0.05) with Se supplementation and the ewes fed with SeY tended (P<0.1) to have higher Se in colostrum than ewes fed with selenite. Although IgG in serum and colostrum of ewes was not affected by supplemental Se, IgM in serum of ewes was increased (P<0.05). Lambs of ewes which were given Se had increased (P<0.05) absorption of IgG, but not IgM. No treatment effects on measures of thermometabolism were detected. In conclusion, Se supplementation of pregnant ewes affected measures of thyroxine metabolism and immunity. Compared to selenite, Se from SeY was more readily transferred to the fetus and colostrum.