EVALUATION OF COBALT PELLETS FOR SHEEP

Vitamin B-12 Concentrations were measured in plasma and liver, and cob alt (Go) concentrations determined in faeces, of sheep given intrarumi nal Co pellets with or without steel grub screws (grinders). The Co pe llets contained 30 or 60% by weight Co oxide (Co3O4) Sheep were mainta ined on pasture at 2 sites in the South East of South Australia in an area where sheep have been shown to respond to Co supplementation. All pellets, apart from one given without a grinder, maintained above-ade quate vitamin B-12 concentrations in liver (>200 nmol/kg wet weight) a nd plasma (>400 pmol/L) for 1 year. In the second year, some pellets c ontaining 30% Co3O4 failed to maintain adequate vitamin B-12 concentra tions in the liver of sheep at 1 site when untreated sheep were at ris k of seasonal Co deficiency (liver vitamin B-12 Concentrations <100 nm ol/kg wet weight). Under these circumstances, a more recently formulat ed pellet containing 30% Co3O4, when given with a grinder, maintained adequate vitamin Bit status of sheep for 3 years. The 'traditional' pe llet containing 60% Co3O4 increased vitamin B-12 Concentrations to hig h normal values (in plasma >1500 pmol/L, in liver >200 nmol/kg wet wei ght) for at least 3 years. Pellets containing 30% Co3O4 may only preve nt Co deficiency for 1 year, depending on the source of the pellets.