The curious case of cobalt…

In the late 19th and early 20th Century, sheep farmers across the world became increasingly aware of a devastating disease that caused their sheep to literally waste away and die.

Initial symptoms of the disease were a general failure of the animals to thrive, they also developed an abnormally coarse fleece. 

The disease went by many names specific to the locality where it occurred.  In the UK it was most commonly called pine, or pining disease – because the animals just seemed to give up the will to live, as though they were pining.  Other names included bush sickness and coast disease.

Stockmen had soon realised that the disease was associated with specific soils and geographic areas.  They also found that if they could move the stock to different pasture, they would sometimes recover with no further intervention. 

Initially, scientists thought the disease was caused by a deficiency of iron.  However, in the 1930s this theory was disproved and cobalt was identified as being the deficient nutrient. 

That’s all a long time ago, but I was reminded of it when the vet at a farm I was working on last year recommended giving the sheep B12 injections.  Coincidentally, at the same time a surprisingly large number of my friends, and their friends and families, had been given vitamin B12 injections by their doctors. 

Few farms bother testing their soils at all, and those that do generally only test for pH (to see if they need to lime) and maybe Phosphorous (P) and Potassium (K).  Hence, few if any would know whether their soils were deficient in cobalt (or any other micronutrient).

And what does that have to do with B12?  Well, cobalt is an essential constituent of vitamin B12; another name of B12 is cobalamin.  In ruminant animals, like sheep, cobalt is needed by the bacteria that live in the animal’s rumen and carry out most of their digestion.  These bacteria also synthesise vitamin B12 which is absorbed by the animal.  So, a deficiency of cobalt is thought to adversely affect ruminants through reducing digestive efficiency and causing B12 deficiency.*

In humans, B12 is essential for red blood cell formation and energy production (amongst lots of other things).  Humans need to obtain an adequate amount of vitamin B12 in their diet and the best natural sources are red meat, eggs, fish and dairy products.  A lack of B12 causes a type of anaemia.

So, maybe if the soil is deficient in cobalt meaning the lambs are needing an injection of B12, perhaps their meat, and the milk products from the dairy herd, are also going to be lower in B12 than might be expected.  And maybe that’s why so many people have been needing B12 injections lately…

The role of cobalt in plant nutrition is poorly understood, except for that in nitrogen fixing plants it plays a critical role for the nitrogen fixing bacteria.  Research is still on-going to find out more about its role in non-nitrogen fixing plants.

The take home message of this story is that the interactions between soil, plants/crops, livestock and human nutrition are incredibly complex and fascinating.  There are at least 15 essential mineral elements involved in plant nutrition – and that number tends to keep on increasing as scientists develop a better understanding of plant nutrition.

* for useful information on cobalt deficiency in sheep see the Teagasc factsheet at http://www.teagasc.ie/newsletters/farmingtips/2009/sheep-20090623.asp

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