Effects of pre- or postpartum selenium supplementation on selenium status in beef cows and their calves

The effect of Se supplementation before or after calving on Se status in de ficient cows and their calves was studied using 72 beef cows in two experim ents. In Exp. 1, cows calving in February or March 1997 were supplemented o rally for 15 d in late pregnancy with 13.0, 32.5, or 45.5 mg of Se/d as sod ium selenite. Glutathione peroxidase (GSH-Px) activities were measured in r ed blood cells (RBC) or plasma of cows and calves at d 15 and between d I? and 88 after calving. In Exp. 2, cows calving in January 1997 were suppleme nted orally with .0, 13.0, or 32.5 mg of Se/d for 15 d postpartum, and calv es were injected with 1.38 mg of Se when 2 d old and at an average age of 4 9 d. The GSH-Px activities were measured in 30-d-old calves and in cows and calves between d 77 and 115 after calving. In both experiments, Se supplem entation resulted in adequate Se status for the dams. The increase in RBC G SH-Px activity was faster with 45.5 mg of Se/d, and GSH-Px activities remai ned high for up to 98 d after the end of supplementation. The improvement i n Se status in calves as a result of maternal supplementation was greater i n Exp. 1 than in Exp. 2, suggesting that the placental transfer of Se is mo re efficient than milk transfer. Prepartum oral Se supplementation of defic ient beef cows with 13.0 mg of Se/d for 15 d allowed adequate Se status of dams and calves, and 45.5 mg of Se/d resulted in a faster improvement of Se status. Parenteral administration of 1.38 mg of Se to newborn calves did n ot sustain normal Se status in calves issued from deficient cows.