Dietary choline requirement of juvenile hybrid striped bass

Two experiments were conducted to estimate the dietary choline requirement and to determine the effects of dietary choline on liver lipid deposition in juvenile hybrid striped bass (Monrone saxatilis x M. chrysops). Experimental diets contained 0.73 g total sulfur amino acids/100 g diet (0.47 g methionine + 0.26 g cyst(e)ine/100 g diet), thus meeting, but not exceeding, the requirement. Graded levels of choline bitartrate in Experiment 1 and choline chloride in Experiment 2 were added to the basal diet, resulting in eight dietary treatments in each experiment. Dietary treatments were 0, 250, 500, 1000, 2000, 4000, 6000 and 8000 mg choline/kg dry diet. Diets were fed for 12 and 10 wk in Experiments 1 and 2, respectively. Dietary choline concentrations significantly affected weight gain, feed efficiency, survival and total liver lipid concentrations in each experiment. Weight gain and feed efficiency were greatest in fish fed 500 mg choline/kg dry diet as choline bitartrate. Total liver lipid concentrations were variable but tended to be lowest in fish fed diets containing at least 2000 mg choline/kg diet. Survival was significantly lower in the group of fish fed 8000 mg choline/kg diet supplied by choline bitartrate. Weight gain and feed efficiency were greatest and total liver lipid concentration was lowest in groups of fish fed at least 500 mg choline/kg diet as choline chloride; survival was unaffected by dietary treatment. Therefore, choline chloride seems to be a better source of dietary choline than choline bitartrate and 500 mg choline/kg diet is adequate for maximum weight gain and prevention of increased liver lipid concentration in juvenile hybrid striped bass.