Corn gluten meal partially replaces dietary fish meal without compromising growth or fatty acid composition of sunshine bass

A 7-week feed trial was conducted to determine the minimum dietary level of menhaden (Brevoortia spp.) meal (MM) needed to maintain growth, fillet quality, and health in sunshine bass (female white bass Morone chrysops x male striped bass M. saxatilis). Sunshine bass were stocked at 10 fish/tank (group weight per tank: mean +/- SD = 182.0 +/- 2.0 g) into each of 28 tanks and were fed seven experimental diets (4 randomly assigned tanks/diet). Experimental treatments ranged from 0% to 24% MM; com gluten meal (CGM) was used as the dietary protein replacement. The isonitrogenous diets contained 41% crude protein and 14% crude lipid, and fish were fed to apparent satiation twice daily. Sunshine bass given diets with less than 20% MM had significantly lower (P < 0.05) weight gain than fish in other treatments; however, specific growth rates and feed conversion ratios remained constant in fish fed diets with as little as 16% and 12% MM, respectively. Total n-3 fatty acids and 20:5(n-3) content of the fillets were similar between the 20% and 24% MM treatments; however, these fatty acids declined as more MM was replaced. Highly unsaturated fatty acid concentrations in the fillet were similar among diets of at least 16% MM. Collectively, our data provide evidence that MM can be substituted with CGM in diets fed to sunshine bass without adversely affecting growth and fillet quality; however, complete replacement of MM adversely affected growth, lipid metabolism, and oxidative stability in the liver. More effective usage of menhaden resources will enable the industry to create economically and environmentally sustainable diet formulations for sunshine bass.