B1 deficiency or thiamine deficiency causes a disease known as polioencephalomalacia (PEM).

In New Zealand this is most commonly seen in youngstock, more specifically calves 6-12 months old and we tend to see this deficiency over the summer months.

So how do cattle take their daily vitamin B1?

Unlike us with most of our vitamins; cattle don't need to actually eat their vitamin B1, but rely on the bacteria found naturally in their rumen to produce it daily. Anything that upsets these bacteria can result in less thiamine being produced and there are some enzymes (found in some plants and produced by some bacteria) that destroy the thiamine while it's in the rumen, these are called thiaminases.

Because the B1 levels in cattle are so dependent on rumen production and health, the most common time we see B1 deficiency in New Zealand is after moving cattle from rough pasture to a lush new paddock. For this reason, it is worth keeping an eye on cattle, particularly youngstock, after moving them onto a fresh paddock after being on more stalky pasture; or to slowly transition them onto nicer pastures.

So what does B1 deficiency look like?

Typically we see B1 deficiency as:

• Depression
• Appearing to be blind
• A lack of coordination
• Champing of jaws and head pressing

These clinical signs are not specific to thiamine deficiency and we should also consider lead poisoning and salt poisoning as well as causes of blindness like malignant catarrhal fever.

For cases of PEM the best method we have to diagnose is seeing whether animals respond to treatment with thiamine/B1 injections, otherwise, post-mortem examination changes can be seen in the brain. Often we can help our diagnosis with history such as a sudden change in feed and that the animals are youngstock.

If we think a calf has B1/thiamine deficiency we need to start treating them straight away, as the damage to the brain can be irreversible, with the first treatment of B1 going into the vein, followed by subsequent injections either into the vein or muscle for at least three days.

This is a relatively frequently diagnosed disease in youngstock by the team here, however, as cattle can show similar signs with other diseases we would definitely recommend giving either the clinic or your KeyVet a call to work out the best plan if you are seeing signs that you think could be due to B1 deficiency.