Effects of dietary creatine on juvenile hybrid striped bass in low-salinity and brackish waters

Abstract

A 12-week, two-part feeding trial was conducted to evaluate the potential benefits of creatine supplementation in the diet of hybrid striped bass (HSB) under different water salinity and osmoregulatory conditions. A basal diet was formulated to contain 40% crude protein, contributed equally by menhaden fishmeal and soy protein concentrate, and 10% lipid. Three isonitrogenous experimental diets were prepared by supplementing 1, 2, and 4% creatine to the basal diet replacing cellulose and adjusting a 50/50 aspartate/glutamate premix. During the first 7 weeks, salinity of the recirculating system was maintained at 3 g/L (low salinity), then, for an additional 5 weeks, switched to 15 g/L (brackish water). No discernable differences in weight gain, feed efficiency, or survival of HSB were observed during the low-salinity phase. However, significant improvements in weight gain were exhibited by fish fed diets supplemented with 2 and 4% creatine compared to those fed basal and 1% creatine diets during the brackish water phase. Muscle creatine levels significantly increased with dietary creatine supplementation during both culture phases. The positive effects of dietary creatine supplementation on HSB appeared to be due to increased energetic demands of the brackish water environment.