Objective: To assess the effectiveness of cobalt pellets in maintaining adequate vitamin B12 in beef cows on pasture of low cobalt content.
Design: A field experiment in a herd grazing cobalt deficient pasture.
Animals: Mature Murray Grey cows.
Procedure: Cows were given a single oral dose of 0, 1, 2 or 4 cobalt pellets (30 g pellets containing 30% by weight cobaltic oxide) with a selenium pellet and a grub screw. Samples of blood, liver, faeces and milk for chemical analysis were collected at intervals over a period of 2 years after treatment.
Results: A single cobalt pellet raised liver vitamin B12 concentration of cows above that of untreated cows for at least 28 weeks, and 2 or 4 pellets for 57 weeks. Plasma vitamin B12 concentration was an unreliable indicator of the effectiveness of cobalt pellet therapy. Milk vitamin B12 and faecal cobalt concentrations increased in response to cobalt pellet therapy.
Conclusion: These studies show that one cobalt pellet will prevent vitamin B12 inadequacy in beef cows for between 28 and 57 weeks; two or four pellets will prevent inadequacy for 57 to 75 weeks. Milk vitamin B12 concentration may be a useful indicator of the effectiveness of cobalt pellets in increasing the vitamin B12 supply in lactating cows.