Effects of Feeding Supplemental Organic or Inorganic Selenium to Cow-Calf Pairs on Selenium Status and Immune Responses of Weaned Beef Calves1

In current marketing channels, calves are purchased with little indication of nutritional status on which a fully functional immune system is dependant. Adequate immune function in recently weaned calves is required for development of disease resistance. At weaning, 18 spring-born steer calves (BW = 200 ± 5.2 kg) were randomly selected from six groups of 20 cows to test the effects ofSe supplementation and source of Se fed pre-weaning on Se status and immune function of calves after weaning. Mineral supplements supplying no Se, 26 ppm of Se from sodium selenite, or 26 ppm of Se from Se-yeast were fed in a free-choice mineral supplement. After weaning, calves were fed bermudagrass (Cynodon dactylon [L.] Pers.) hay and 1.40 kg of supplement daily. Selenium status and immune characteristics of calves 22 d after weaning were tested by analysis of whole blood Se, glutathione peroxidase (GTH-Px) activity, lymphocyte proliferation, macrophage phagocytosis, and interferon-γ (IFN) production. In vivo cell-mediated immunity was tested by skin-swelling response to an intradermal phytohemagglutinin (PHA) injection. Whole blood Se concentrations and GTH-Px activities (54.7 ppm and 40.2 Eu/gHb, respectively) suggested Se deficiency of control calves. Supplementation with Se increased (P<0.01) whole blood Se concentration and GTH-Px. Seleniumyeast increased (P<0.01) whole blood Se concentration and macrophage phagocytosis compared with sodium selenite. In vivo cell-mediated immune response tended (P=0.12) to increase with Se supplementation. Supplementation of cow herds with Se before weaning increases Se status of weaned calves in areas where Se deficiency may be a problem.