Physiological effects of dietary silver sulfide exposure in rainbow trout

Silver accumulation was examined in juvenile rainbow trout during a 58-d fe eding study with silver sulfide ((AgS)-S-2) added to the diet at concentrat ions ranging from 0 to 3,000 mg/kg Ag. Silver in the livers of fish fed the 3,000-mg/kg diet reached a level approximately fourfold higher than the co ntrol, representing an initial accumulation rate of 9.5 ng/(g.d). Despite t his increase in silver levels in the liver, no influence of liver copper le vels was observed. In comparison, there were no significant elevations in s ilver burdens in the kidneys, gills, or intestines, apart from a transient increase in the gills of fish fed the 3,000-mg/kg Ag diet on day 24 only. D aily food consumption rates were lowered by 14 to 22% in all the Ag2S treat ments relative to control levels, possibly because of the decreased palatab ility of the Ag-laden diets. However, there were no significant differences in growth rates between any of the treatments for the duration of the stud y, suggesting a lack of any physiological perturbation by dietary Ag2S expo sure. The results of this study suggest that dietary silver sulfide exposur e at or below 3,000 mg/kg Ag is physiologically benign over a 58-d period.