Experimental thiamine deficiency in captive harp seals, Phoca groenlandica, induced by eating herring, Clupea harengus, and smelts, Osmerus mordax

Abstract

Freshwater smelts, and Atlantic herring, both shown to contain thiaminase, were fed to harp seals under a variety of experimental conditions. When thiamine was not administered, the seals developed thiamine deficiency which, in some cases, was fatal. Red blood cell transketolase was effective in demonstrating deficiency.In a controlled experiment, three seals ingesting smelts died within 80 days; two showed terminal signs of central nervous system disturbances and concomitant plasma electrolyte imbalance. Seals fed a diet of thiamine-free herring survived despite biochemical evidence of deficiency. This is attributed to the high fat content of herring.Thiamine administered either intramuscularly or orally, during the course of deficiency, effected prompt recovery. Thereafter, seals maintained on herring required 25–33 mg thiamine/kg of ingesta, if the vitamin was consumed in the diet; if administered 2 h before feeding, 35 mg/day was sufficient for normal maintenance.