[Cobalt supply to ruminants, a bottleneck?]

On some dairy farms the supply of cobalt was expected to be adequate given the soil data and the composition of the ration. However cows on these farms produced less milk than expected and their condition was poor considering their ration and milk yield. The milk lactose content was less than 4.5%. The cows produced more milk after they were given extra cobalt (5.5 mg/day). The animals, condition improved, the milk lactose content rose, and the animals ate more dry matter than previously. A marked increase in the potassium content of the grass silage possibly depressed the availability of cobalt and caused vitamin B12 deficiency. This needs further investigation.