Vitamin B1 (Thiamine)

Vitamin B1, or thiamine, is critical for metabolism because of its role in processing fats, proteins, and carbohydrates.  This makes vitamin B1 a nutrient that is necessary for the health of all cells, but it is especially important to the brain.

Natural Sources

Grazing animals will naturally produce their own vitamin B1 if provided with quality forage.

Other animals, such as swine and poultry, can use the vitamin B1 that is found in cereal grains.  Among the grains, barley is considered the best source of thiamine, followed by wheat, oats, and corn.  Wheat bran, peanut meal, soybean meal, and cottonseed meal also contain this vitamin.  The most potent source of vitamin B1, however, is brewer’s yeast.

In addition to the grain and yeast sources above, pets can also obtain thiamine from liver and cooked meats, particularly pork.

Causes of Deficiency

Vitamin B1 (Thiamine)
Bracken fern

Stress can cause a vitamin B1 deficiency in livestock, but there are a number of dietary reasons that an animal might have a deficiency.  Cobalt and copper deficiencies can lead to thiamine deficiency.  In grazing animals, processed high-carbohydrate feeds can cause rumen bacteria to break down the available thiamine in the gut, particularly if the change in diet is made suddenly.  Pets may suffer from thiamine deficiency if they eat diets high in raw fish or rice bran, both of which contain an enzyme which breaks down thiamine.

Toxicity often leads to vitamin B1 deficiency.  Feed or water containing large amounts of sulfur is one possible cause.  A number of weeds may also spark a thiamine deficiency, including horsetail, bracken fern, and prostrate pigweed, among others.

Feeds that have been highly processed may lose their thiamine content.  This vitamin is sensitive to heat, water, oxygen, alkali, and radiation.

Other causes of deficiency include sulfites, antibiotics, some wormers, coccidiosis, intestinal disease, and bacterial infection.

Symptoms of Deficiency

Thiamine deficiency is typically (but not invariably) noticed in young animals.  It comes in two forms, subacute and acute.

An animal showing symptoms in the acute category will die in less than 72 hours if untreated.  The success of treatment will depend on how badly the brain has been damaged.


  • Malaise/failure to thrive.
  • Separation from the rest of herd or flock.
  • Decreased body temperature.
  • Excessive drooling.
  • Scarlet streaking inside mouth.
  • Hair loss.
  • Head tremors and ear twitching.
  • Slow breathing.
  • Muscle atrophy.
  • Consumption of feces in dogs.
  • Loss of appetite.
  • Weight loss.
  • Vomiting.
  • Brief episodes of profuse diarrhea.
  • Staggering.


  • Stupor.
  • Agitation.
  • Extreme aggression.
  • Persistent crying in cats.
  • Rubbing or pressing head on posts and other objects.
  • Head retraction.
  • Grinding teeth.
  • Dilated pupils.
  • Blindness.
  • Arched back.
  • Spastic, high-stepping gait.
  • Paralyzed toes in poultry.
  • Loss of balance.
  • Inability to stand
  • Convulsions.
  • Coma.

Symptoms of Toxicity

Because vitamin B1 is water-soluble, toxicity is extremely unlikely to occur.  There are a few reports of allergic reactions in pets, but these cases are few and far between.

Medicinal Uses

Vitamin B1 is usually available by prescription only, although side effects are extremely rare.  It is a safe remedy for neurological problems, and has been used with success to calm nervous horses.  Some studies indicate that vitamin B1 may increase both overall milk production and yields of protein and butterfat in dairy cattle, but further research is needed at this point.  In pets, it is sometimes helpful in treating lead and antifreeze poisoning.

Content regarding medical conditions and treatment is provided for general information purposes only, and is not to be construed as legal, medical, or professional advice.  Please consult your veterinarian for advice regarding your specific animal’s needs.

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