lambs in grass

When farm animals were first introduced to NZ from Europe, they didn't thrive. They were sickly and farmers called them ‘Bush Sick’ and assumed that farming in NZ was not a practical proposition. Today, we are known as an agricultural nation. So what happened?

Cobalt deficient soils

Parts of New Zealand have soils that are deficient in the trace element Cobalt. If the soils are deficient, the pasture will be deficient and in turn, the animal will be deficient. In the 1930s Cobalt deficiency was prevalent in NZ, it was known as Bush Sickness in areas that were mainly pumice soils, Morton's Mains Disease in Southland, and Glenhope Ailment in Nelson. Ill thrift in young animals was and still is the main symptom.

Other soils that can be cobalt deficient are those that have had intensive, prolonged cropping, or when there is lush fast growth as in Spring time.

But really, it’s all about Vitamin B12

Although Cobalt deficient soils are the cause, it’s really what the animal uses the Cobalt for that is the issue and that’s where Vitamin B12 comes in.

Vitamin B12 is essential for the growth and good health of all animals, including our farm animals, particularly young lambs, calves, kids, and fawns. B12 deficient, sickly, anemic animals are what caused the early farmers to despair and label NZ as bush sick. 

So, where do farmed animals get Vitamin B12 and how do we tell if our animals are deficient?


When ruminants ingest Cobalt in pasture, they create Vitamin B12. The B12 is created by the microorganisms in the rumen and is stored in the liver. It’s used for metabolizing carbohydrates (energy), lipids, some amino acids, and DNA.

As grazing animals make Vitamin B12 from Cobalt, it has to come from pasture (via the soil), or be provided in the form of supplementation like injection or a rumen bolus.

A young ruminant receives an initial store of vitamin B12 through the placenta before birth. It does get some via the mother’s milk, but by the time the animal is around five weeks old, the store has depleted and it will need to start making its own. This is when deficiencies start to show up.


Pigs and poultry don’t have the organisms in their digestive system that convert Cobalt into Vitamin B12 so they must derive the vitamin directly from their diet, as we do. Humans derive B12 from animal products such as meat, fish, eggs, and dairy. Non-ruminant farm animals can get B12 from the bugs and creepy crawlies and kitchen scraps that form part of their diet, but most reliably it will come from a commercial feed.

Commercial foods are formulated to meet the dietary requirements of pigs and poultry and supply the correct amount of Vitamin B12 so generally, deficiency is not a problem.

Horses, although they are not ruminants, can convert cobalt to B12 and are therefore at the same risk as other animals in cobalt-deficient areas.

Signs of Cobalt/Vitamin B12 deficiency

As Vitamin B12 is essential for the metabolism of carbohydrates and therefore an energy supply, the most noticeable deficiency symptom will be failure to thrive. That is, growth rates will be poor, the animal may not have an appetite and it may be anemic.

Lambs are most susceptible to Vitamin B deficiency, followed by calves, kids, and then fawns. Adult sheep and cattle are generally not affected, but the demands of pregnancy and lactation can affect some adult animals.

How can we tell if our animals are Cobalt/Vitamin B12 deficient?

You can ask your vet to take blood tests at weaning. You can also get liver samples when the animals go to the works.

The good news!

You can’t overdose on B12 - any excess in the body is just excreted in the urine - so you can give supplements without worrying about having to test your soil or animals.

You can treat deficient animals either by a long-acting B12 injection, short-acting injections given monthly, or by giving them a bolus into the rumen. The bolus will last up to 12 months if it isn’t regurgitated.

Just as a boost or to support sick animals you can give an injection or feed one of the many animal health tonics or supplements. There has been a study that shows the benefits of giving B12 to lambs including reducing flystrike.

Generally speaking, adult cattle and sheep shouldn’t need any supplementation. Remember the symptoms of Cobalt deficiency can be similar to other nutritional and health problems, so the best thing to do is to speak to your vet and discuss the need for testing for a Vitamin B12 deficiency and to rule out other causes of poor growth and ill thrift.      

You’ll be amazed

An injection of Vitamin B12 can make a huge difference to an animal that isn’t 100%, it can be an instant pick-me-up. With no danger of overdosing, it’s something you should have at hand and use liberally.