This was first reported on the Chastek Fox Farm in Minnesota in 1936. It is due to this vitamin being destroyed in the feed. Certain fish contain the destructive enzyme known as thiaminase. Common ones include smelt, alewife, sucker, saltwater herring and bullhead. Most saltwater fish such as cod, haddock, redfish and mackerel are safe to feed.
The enzyme can be destroyed by cooking fish at 100°C for 15 minutes. Positive fish should be avoided, if possible, although they can be fed 2-3 days per week if alternated with negative fish. Other items such as liver, meat, brewer’s yeast and wheat germ are high in thiamine.
Indirect deficiencies may happen if cod racks are fed and not cleaned. some stomachs contain thiaminase positive fish or shellfish so still destroy the B, when mixed in the ration.
The first symptom may be refusal to eat followed by staggering and death. Depression and weight loss are also seen.
Treatment is to inject vitamin B1. Rapid recovery is usually seen, especially in early cases. The source of the thiaminase must also be removed from the diet.