Welcome back for this post in my series the ABC’s of vitamin deficiencies.
There are a lot of Vitamin B’s. Today we’ll focus on Thiamine deficiency or Vitamin B1 deficiency.
Again, I’ll be focusing on those food producing animals. It can happen in your cat and dog patients, but I have not seen it. I did see it in a dairy calf.
Clinical signs in calves are neurologic, maybe ataxia (stumbling), opisthotonos (the head being craned backwards), head pressing, and blindness, leading to anorexia, severe dehydration, collapse and death if not treated quickly.
Thiamine deficiency is one of the causes of polioencephalomalacia. Say that ten times fast!
If diagnosed early, treatment with thiamine can reverse the signs. It is most common in young ruminants that do not have a well-developed rumen. They depend on thiamine in their food, not as in adult cattle where the rumen microbiome contributes to the thiamine needed for life. Bacterial organisms that have thiaminase can also cause thiamine deficiency if there is overgrowth in the rumen.
Remember, vitamins are cofactors for enzymes. Ahhhh good ol’ biochemistry! I’m having flashbacks from my biochem course. It’s a tough subject. Regardless, it’s something that you should know for your board examinations.
Oddly enough, I also remember, both during my zoo keeping days and in my vet school days, injecting thiamine paste into herring to feed to pelicans. Freezing, storing and thawing fish can cause a decrease in thiamine, so thiamine needs to be supplemented for piscivorous animals in captivity. Back to calves, thiamine is a cofactor for many enzymes in cellular metabolism. Well, for all animals, not just calves. The bolded enzymes in the diagram require thiamine. If the enzyme pyruvate dehydrogenase is slowed due to a lack of cofactor then pyruvate cannot be converted to Acetyl CoA. This kicks in anaerobic metabolism creating lactate from pyruvate. An elevation in lactate leads to an increase in acidity of the blood taxing the acid-base balance of the body, eventually leading to cell death. Fun.
Thiamine deficiency is not just a matter of making sure your cattle get enough thiamine. You have to watch that the cattle are not consuming plants with thiaminase or high sulfur (Brassica), as this also affects thiamine absorption.
Thiamine can be given by injection, or by oral drench. Calves with minimal signs may recover 100% within 48 hours. Water soluble B vitamins will get flushed out in the urine if you have too much thiamine, so unlike Vitamin A, you won’t overdose your patient on Vitamin B1.
That’s it for now. Stay tuned for more ABC’s of Vitamin Deficiencies!