The influence of diet and preexposure on the tolerance of sodium pentachlorophenate by rainbow trout ( Salmo gairdneri)

Abstract

The combined effects of diets varying in carbohydrate-lipid ratio, as well as preexposure to sublethal levels of sodium pentachlorophenate (NaPCP), on the lethal tolerance of waterborne NaPCP by rainbow trout ( Salmo gairdneri) were examined. The three diets used were practical salmonid formulations, equivalent in energy and protein content, with cerelose-fish oil ratios of 18.2:4.7% (high carbohydrate, HC) 9.3:9.1% (intermediate, INT), and 0.6:13.8% (low carbohydrate, LC). Trout that had been reared on the test diets for 12 wk, were exposed to 0 or 50 μg NaPCP·1 −1 for the following 26 d. The incipient lethal level (ILL) of NaPCP for the three control groups (211 μg·1 −1, LC; 221 μg·1 −1, INT; 224 μg·1 −1, HC) and the NaPCP preexposed HC group (208 μg·1 −1) were not significantly different. The ILL of NaPCP for the LC (182 μg·1 −1) and INT (190 μg·1 −1) NaPCP preexposed groups were significantly less than for the other groups, but not different from each other. Within each preexposure level, strong correlations were noted between the ILL of NaPCP and the diet-dependent parameters liver somatic index, liver glycogen content, liver protein content, and whole-body lipid content. Dietary lipid content appeared to be the primary feed component affecting the tolerance of NaPCP.