Evidence of a thiamine deficiency in sheep fed maize silage.

Two groups of Merino sheep (with or without rumen fistulae) were used to study the effect of feeding maize-silage (compared to hay) on: thiamine concentrations in rumen fluid, tissues and organ; blood transketolase activity; microbial fermentation in the rumen. After sheep were transferred from a hay diet to maize-silage, thiamine concentrations in ruminal fluid fell to about 25% of control values on hay. Thiamine levels greatly decreased in kidney, heart, liver, rumen tissue and large intestine. Blood transketolase and TPP effect significantly decreased (P less than 0.01). Ruminal ammonia nitrogen and total volatile fatty acid (VFA) concentrations were not affected by the two diets. However, both butyric acid and isovaleric acid were significantly higher (P less than 0.001) in rumen fluid of sheep fed maize-silage. No significant differences were detected between diets for ruminal thiaminase activity regardless of the time of sampling. Relationships between butyric fermentation, thiaminase activity in maize-silage diet and a possible role of Clostridium are discussed. It was concluded that there is a marked thiamine deficiency in sheep fed maize-silage; the factors involved need further study.