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 hormo nes, Se in tissues, immunoglobulins (Ig) in serum, and measures of thermome tabolism in ewes and their newborn lambs. Pregnant ewes (n = 21) were rando mly assigned to receive a diet deficient of Se (<0.02 ppm) or supplemented to provide 0.3 ppm Se from either sodium selenite or selenized yeast (SeY). Pregnant ewes which were fed additional Se had increased (P < 0.05) concen trations of Se in whole blood and serum, greater activity of glutathione pe roxidase (GSHpx), and higher conentrations of tri-iodothyronine (T-3) and t hyroxine (Ti). At 12 h of age. lambs of ewes given Se had higher (P < 0.05) concentrations of Sc in blood and liver, greater activities of GSHpx, and tended (P < 0.1) to have higher T-3 levels. When the two So supplements wer e compared, lambs of ewes which were fed with SeY had higher (P < 0.001) co ncentrations of Sr and activities of GSHpx (P < 0.05) in blood than lambs o f 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 effec ts on measures of thermometabolism were detected. In conclusion, Se supplem entation of pregnant ewes affected measures of thyroxine metabolism and imm unity. Compared to selenite, Se from SeY was more readily transferred to th e fetus and colostrum. (C) 2001 Elsevier Science B.V. All rights reserved.