The effects of injectable sodium selenite on immune function and milk production in Sardinian sheep receiving adequate dietary selenium

The aim of this preliminary study was to determine the effects of selenium (Se) injection on Se status, cell-mediated immunity (CMI), milk yield and m illi somatic cell count (MSCC) of ewes fed adequate amounts of Se, and on S e status, passive immunization and CMI of their offspring. Thirty days befo re lambing, 36 Sardinian ewes were assigned to one of three groups. One gro up (NT) was not treated; a second group (BL) was given 5 mg of Se on day 30 before lambing; a third group (BLL) was given 5 mg of Se on day 30 before lambing and at lambing. Selenium was given intramuscularly as sodium seleni te. Selenium status was assessed by measuring glutathione peroxidase activi ty of erythrocytes (GSHpx-E). The CMI was measured by determining the incre ases in double skinfold thickness after intradermal injection of phytohaema gglutinin (PHA). Compared to their NT counterparts, ewes belonging to BL an d BLL groups and their offspring had significantly higher GSHpx-E (P < 0.01 ). The GSHpx-E values of lambs were positively related to those of their mo thers (P < 0.0005). Ewes of group BL had a greater (P < 0.01) response to P HA 6 h after injection than ewes of the NT group. Lambs born to BL and BLL, ewes had a greater (P < 0.0001) response to PHA 24 h after injection. Resp onses of ewes and lambs to PHA 24 h after injection were positively related (P < 0.05). Serum immunoglobulin at 10 days of age did not differ signific antly among the three groups of lambs. Compared to the NT group. milk yield on day 70 of lactation was significantly higher in BL ewes (P < 0.05). The MSCC was not affected significantly by Se injection. Immunoresponsiveness and milk yield might represent additional and appropriate criteria to consi der when re-evaluating Se requirements of dairy sheep. (C) Inra/Elsevier, P aris.