Reaction cements as materials for the sustained release of trace elements into the digestive tract of cattle and sheep. II. Release of cobalt and selenium.

Acid-base reaction cements, containing salts of copper, cobalt and selenium, were placed in the reticulum of sheep and cattle, and the rate of release of cobalt and selenium from them was measured. The rate of release of cobalt decreased with time but was sufficient to provide adequate supplementation for at least 6 months. After an initial rate of release of 4 mg Se/day for 1-2 weeks, the mean subsequent rate of release of selenium over a period of 4 months was 0.1 mg Se/day (identical to 5 micrograms Se/day/cm2 surface area). Field trials in lambs and growing steers showed that the cement increased the selenium concentration of their blood throughout a summer grazing period.