Sheep farmers are advised to be wary of misleading ‘go faster stripes’ on supplements for weaned lambs that claim vitamin B inclusion.

This warning comes from vet Dr Elizabeth Berry, veterinary director at Animax.

She said: “For ruminants, supplementary B-vitamins are no more than pixie dust. As long as the diet contains sufficient cobalt, ruminants make their own B12, for example.

“Moreover, vitamin B1 and most others in this group are also made by rumen bugs as long as rumen function is good. At best, inclusion in a supplement is a placebo.”

For farms producing finished lambs, Dr Berry said getting them to target weight as quickly as possible without concentrates clearly makes good business sense. Among factors governing the conversion of grass into meat, she advises that one of the most critical in lambs is the role of cobalt.

“In all ruminants, cobalt is essential for the synthesis by rumen bacteria of vitamin B12, which is critical in energy and protein metabolism,” she said. “While lambs are suckling, milk provides their cobalt requirement in full. But post-weaning, cobalt levels in grass are deficient in many parts of the country.”

Dr Berry said heavy rainfall in February and March will have leached cobalt from topsoil.

“Since then, of course, we’ve seen rapid grass growth, but the resulting dilution effect creates extra-low cobalt levels in herbage,” she said. “So, for maximum growth rates off grass, supplementation is even more important than usual.”

For convenience and reliability, Dr Berry recommended either a pure cobalt, or cobalt-selenium-iodine combination, trickle charge leaching bolus. Both of these, Tracesure Cobalt and Tracesure Lamb Finisher, contain premium cobalt sources with high bioavailability, which is not universally the case.

“To avoid doubt,” she said, “these boluses do not contain B-vitamins because, as long as cobalt inclusion is sufficient, they’re unnecessary.”