Effect of a copper, cobalt and selenium soluble glass bolus given to grazing sheep

Three field trials were carried out to evaluate the performance of a sintered soluble glass copper, cobalt and selenium bolus for maintaining adequate levels of the three trace elements. Trial 1 used 34 growing lambs, trial 2 used 36 growing lambs whilst trial 3 used 50 year-old non productive female sheep. In each trial half the sheep had a bolus administered (bolused) and half remained as controls. Blood samples were taken immediately prior to bolus administration and then at regular intervals throughout each trial. The samples were analysed for copper status (serum caeruloplasmin activity and plasma copper concentration), cobalt status (serum vitamin B12 concentration) and selenium status (erythrocyte glutathione peroxidase activity). For trial 1 the bolused sheep at all post treatment samplings (days 20, 42 and 63) were significantly increased in both cobalt and selenium status (P