Cobalt and Vitamin B12

What are the relative merits or otherwise of cobalt compared to vitamin B12 supplementation in dairy cattle”?

There is frequent debate about the best way to manage a herd’s requirements for cobalt or vitamin B12. Supplemental cobalt can be provided by top-dressing, in salt licks or feeds, as sustained release boluses, and by drenching with a cobalt salt. Vitamin B12 supplementation can only be provided by injection.

Whatever means is employed, the objective is to ensure cattle maintain adequate liver vitamin B12 levels to enable their production of glucose and energy from propionic acid. Cobalt is essential for rumen micro-organisms to synthesise vitamin B12. To ensure sufficient vitaminB12 production, it is generally considered that lactating dairy cattle require a minimum dietary content of 0.1ppm cobalt or about 10mg cobalt/cow/day. The liver (the main storage organ for B12) is considered to have adequate levels of vitamin B12 when it contains not less than about 350nmol/kg of the vitamin.

So how is it best to ensure this optimal cobalt intake, or to ensure the necessary B12 liver reserves are maintained?

The merit of B12 injections is that you know exactly how much vitamin you are giving., So, if you know the herd’s average liver B12 status (eg. from liver biopsy), you can work out how much to give to fill their liver reserves without wasteful over-dosing. One injection will provide adequate levels for 1-3 months. A prolonged release injection is now available that is said to maintain levels for 4-6 months.

The downside of B12 injections can be the cost and any hassles associated with giving the injections. As well, one cannot be exactly sure how long adequate B12 reserves will be maintained after injection. The vitamin can be utilised at different rates by different animals, and utilisation varies depending on the stage of lactation and the animals’ overall health demands for B12.

Ensuring there is adequate cobalt for rumenal bacteria to use to manufacture B12 is a more natural way to maintain B12 requirements. If it is practical to give supplemental cobalt regularly in the diet, then a very consistent supply of B12 will be made available to the animals, and one can be more confident B12 levels will remain optimal whatever the circumstances.

An added merit for cobalt supplementation is that it is provides benefit to the rumen bacteria as well as the animal. Rumen bacteria require cobalt and B12 themselves, and cobalt supplementation increases the number of bacteria in the rumen. Many nutritionists now provide for 1-2 ppm cobalt in the diet, (considerably above the 0.1 ppm minimal recommendation). This is considered to help increase fibre digestion and nutrient utilisation, probably due to its positive effect on the microbial population.

Ultimately, the choice between giving B12 injections or supplemental dietary cobalt depends on preference and practicality. And of course, cost versus the perceived benefit. Regular daily supplementation with a cobalt salt supports both the animal and its bacterial colony, whereas B12 injection primarily assists the animal only. Organic cobalt salts such as cobalt glucoheptonate are more soluble than inorganic salts like cobalt sulphate, and may have better availability to the bacteria.

In general, daily cobalt supplementation will prove cheaper than B12 injection when comparing the cost of maintaining adequate B12 levels in milking stock over a full year. For calves and yearlings however, where it can be difficult to ensure a regular intake of cobalt, B12 injection may be the better option.