Dietary replacement of fishmeal with commercial protein blends designed for aquafeeds in hybrid striped bass (Morone chrysops ♂× Morone saxatilis ♀): Digestibility, growth, body composition, and nutrient retention

Abstract Four commercial protein blends—Elite 60™, Elite 65™, Elite 70™, and Pro-Cision™ (HJ Baker & Bros., Inc., Tuscola, Texas, USA)—were evaluated in hybrid striped bass (HSB) for nutrient digestibility and fishmeal (FM) replacement value. A control diet was formulated like a commercial HSB feed containing 17% FM that met or exceeded the nutritional requirements of HSB. Commercial blends replaced FM in the control diets on an ideal protein basis by supplementing the first-three limiting amino acids (methionine, lysine, threonine). Diets were formulated on a digestible protein basis (38% digestible protein), isolipidic (16%), and contained 10% lipid from marine fish sources. Fish fed the control diet generally exhibited better growth and nutrient utilization responses than the other diets. Responses to the Elite™ products were intermediate, while Pro-Cision™ lagged in both digestibility and growth responses. Digestibility of gross nutrients in each of the test products did not differ significantly from those of FM, but protein was significantly more digestible in Elite 70™ compared to that of FM and Pro-Cision™. Availabilities of leucine, phenylalanine, tyrosine, and valine in Pro-Cision™ were significantly less (92.2%, 91.3%, 91.0%, and 91.5%, respectively) than those in FM (96.1%, 96.8%, 94.6%, and 94.5%, respectively). Fish fed the Pro-Cision™ diet exhibited significantly lower cumulative feed intake, average weight, and muscle ratio compared to fish fed all other diets. Elite 60™, Elite 65™, and Elite 70™ fish did not differ in intraperitoneal fat or muscle ratio compared to fish fed the control diet. Fish fed all three Elite™ diets had significantly lower average weight (52.5–57.9 g) compared to fish fed the control diet (73.2 g). There were no differences in arginine and histidine whole-body nutrient retention among dietary treatments, while other nutrient retention efficiencies did differ across treatments. Nutrient retention of the averaged essential amino acids was not significantly different in fish fed Elite 70™ compared to fish fed the control diet. There were no significant differences in lysozyme activity and mean corpuscular hemoglobin concentration among treatments. It appears that Pro-Cision™ is not an attractive alternative to FM in HSB diets considering total feed intake, growth, and nutrient and energy retentions. However, Elite 65™ and Elite 70™ may be potential FM alternatives in HSB diets despite differences in growth performance after 13-weeks.