Studies on the use of novel selenium- and cobalt-containing rumen boluses for cattle and sheep

Studies in both beef cows and in growing cattle showed that two novel 18g high density sustained-release reticulo-rumen boluses providing totals of 1656mg Se as sodium selenite and 4590mg Co as cobalt carbonate significantly increased blood glutathione activity for at least one year. Responses in blood glutathione activity were comparable to those found in earlier studies with existing multi-trace element/vitamin sustained release boluses in wide commercial use. Serum vitamin B-12 concentrations did not reflect cobalt release as the determination is of limited diagnostic value for cattle blood. In one study with ewes having a past history of poor lambing performance, the previous incidence of yeld ewes (13.6%) was significantly reduced to 7.2% by giving before mating a single 6.0g bolus containing 276mg Se (as sodium selenite) and 765mg Co (as cobalt carbonate). There was an accompanying significant increase in the proportion of ewes with twin lambs from 20.1% to 25.3% of the flock. There were very significant responses in both blood glutathione activity and serum vitamin B-12 concentrations assessed 122 days after bolus administration. Very similar results for enhanced lambing performance and responses in blood analyses were found when comparable ewes were given a single existing commercial sustained release multi-trace element/vitamin bolus plus a grinder.