Comparison of transketolase activity and thiamin pyrophosphate levels in erythrocytes and liver of rainbow trout (Salmo gairdneri) as indicators of thiamin status.

Yearling rainbow trout (Salmo gairdneri) were fed a purified diet with and without thiamin supplementation for 30 wk, at which time overt signs of thiamin deficiency appeared in the deficient group. Overt signs of thiamin deficiency were anorexia, darkening and ataxia. Death rapidly followed the development of overt thiamin deficiency. Transketolase activity and thiamin pyrophosphate levels were measured monthly in erythrocyte and liver samples. Significant differences in erythrocyte transketolase activity between fish fed the thiamin-deficient and control diets were measured after 24 wk of feeding. No significant difference in liver transketolase activity was found between trout fed diets with or without thiamin supplementation. Thiamin pyrophosphate levels were significantly lower in erythrocytes and liver of fish fed the thiamin-deficient diet after 16 wk of feeding. Thiamin pyrophosphate levels in erythrocytes and liver were found to be a more sensitive indicator of thiamin status of rainbow trout than erythrocyte or liver transketolase activity.