Physiological effects of dietary silver sulfide exposure in rainbow trout
Silver accumulation was examined in juvenile rainbow trout during a 58- d feeding study with silver sulfide (Ag2S) added to the diet at concentrations 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 control, representing an initial accumulation rate of 9.5 ng/(g·d). Despite this increase in silver levels in the liver, no influence of liver copper levels was observed. In comparison, there were no significant elevations in silver 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. Daily food consumption rates were lowered by 14 to 22% in all the Ag2S treatments relative to control levels, possibly because of the decreased palatability of the Ag-laden diets. However, there were no significant differences in growth rates between any of the treatments for the duration of the study, suggesting a lack of any physiological perturbation by dietary Ag2S exposure. The results of this study suggest that dietary silver sulfide exposure at or below 3,000 mg/kg Ag is physiologically benign over a 58-d period.