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Vitamin B1/Thiamine Deficiency (Polioencephalomalacia)


This is a disease seen mainly in calves but occasional outbreaks may occur in milking cows. Ruminants like cows need the bacteria in their rumen to produce thiamine. Deficiency happens usually due to thiaminases (bacteria which destroy thiamine) being produced in the rumen. These are usually produced by a change in the “Rumen Microflora” or indirectly from plant sources. Animals are often affected following a change from poor, stalky pasture to a diet of good lush pasture.  In grazing cattle in New Zealand the disease is seen most often in young stock in mid summer, but here in the South Waikato it is also common in weaner calves.


A continual supply of thiamine is needed for normal brain function. If there is an insufficiency, this leads to cellular changes which eventually lead to brain swelling and thus death of brain cells. It is this brain swelling that is responsible for the clinical signs.  If the condition is not treated, animals will likely die.


Affected calves tend to isolate themselves, don’t eat, and may develop diarrhoea, become wobbly, show abnormal eye movement with some head tremors. The calves appear blind and may head press. As the signs progress the calves go down, develop tremors, go stiff. As they don’t eat or drink they become dehydrated. If animals are not treated quickly they will die.


Other diseases that cause similar clinical signs may include:

  1. Bacterial brain diseases e.g. Salmonellosis, Listeria (Circling Disease)

  2. Enterotoxaemia (Pulpy Kidney)

  3. Excess dietary sulphur

  4. Salt poisoning/water deprivation


Diagnosis of polioencephalomalacia is usually made based on clinical signs and response to treatment.


For best chances of survival, affected animals must be treated immediately. Brain cells die by the millions in a very short time. Injections of Vitamin B1 (B calm®/Duoject-B®) and penicillin (Intracillin® or Depocillin®) are required to prevent further death of brain cells and cover bacterial infections. Calves that respond to treatment may fully recover within 12 hours while some may still have some residual blindness or even permanent brain damage.


Suggested Treatment protocol:


B CALM®/Duoject-B® (Subcutaneous or intramuscular)

          Day 1Day 2       Day 3

Calf 100-150kg LWT10ml AM         10ml AM      10ml AM

         10ml PM          5ml PM       5ml PM


INTRACILLIN® or DEPOCILLIN®  (Intramuscular injection)

          Day 1Day 2       Day 3

Calf 100kg LWT7ml AM7ml AM       7ml AM

         7ml PM7ml PM       7ml PM

Calf 150kg LWT10ml AM         10ml AM       10ml AM

         10ml PM         10ml PM       10ml PM


In some cases, recovery may take up to 7 days, but most animals will show improvement within 24 hours.


Prevention and control of this disease can be difficult due to its sporadic nature. If the source of an outbreak is identified (e.g. low fibre, high starch diet or excess sulphur in feed) removal from this feed should be undertaken.


(ref- Large animal internal medicine 2nd edition, Diseases of cattle in Australasia).

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Vitamin B1 Deficiency