Trace element deficiencies are common in many countries and affect animal health, productivity and welfare. Trace elements that can be limiting in animal nutrition include copper, cobalt, selenium and zinc. Deficiency diseases may be manifested as a consequence of a single or a multiple element deficiency. Deficiency in any of the above trace elements can result in an increased disease susceptibility and a decreased immune function. A soluble glass bolus has been developed for the sustained release of zinc, cobalt and selenium to sheep, using the same technology as the commercially available copper, cobalt and selenium bolus (Cosecure). The aim of this experiment was to observe whether the trace elements released from the bolus would have an effect on the immune function of sheep, as measured by the humoral immune response to a novel antigen.