Effects of Dietary Selenomethionine on Cutthroat Trout (Oncorhynchus clarki bouvieri) Growth and Reproductive Performance Over a Life Cycle

A 2.5-year feeding trial was conducted in which cutthroat trout (Oncorhynchus clarki bouvieri) were fed either a basal diet (1.2 mu g Se/g diet) or the basal diet supplemented with 2, 4, 6, 8, or 10 mu g selenomethionine/g diet from 1 g weight to maturation. After 44 weeks of feeding, a subsample of fish was removed from dietary treatment groups and fed the basal diet for an additional 32 weeks. Concentrations of Se in whole fish and eggs increased in proportion to dietary Se intake, but no differences in growth, feed intake, survival, or egg hatchability were observed among dietary groups. Cranial-facial deformities in second-generation offspring were less than 6% in all treatment groups except for fish fed the diet supplemented with 4 mu g selenomethionine/kg, for which a 9.2% incidence was observed. Fish switched from selenomethionine-supplemented diets to the basal diet lost Se, calculated as mu g Se lost/g weight gain, at 1.01, 2.84, 4.42, and 4.42 for dietary treatment groups 3, 4, 5, and 6, respectively. Results suggest no toxicity of dietary selenomethionine up to 10 mu g/g supplemented diet and that with total life-cycle exposure, cutthroat trout increase Se excretion to maintain whole-body concentrations below toxic levels.