Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2008
Publication Date: 3/13/2009
Citation: Rawles, S.D., Gaylord, T.G., McEntire, M.E., Freeman, D.W. 2009. Evaluation of poultry by-product meal in commercial diets for hybrid striped bass (Morone chrysops X M. saxatilis) in pond production. Journal of the World Aquaculture Society. 40:141-156. Interpretive Summary: Fish feeds contain fishmeal as a major ingredient because it is a high quality protein. Fishmeal is a limited resource and competitive markets in the animal feed industry also raise the price. The aquaculture industry is extremely interested in reducing the amount of fishmeal in fish feed. We tested commercial diets for hybrid striped bass (HSB) in which poultry by-product meal (PBM), instead of fishmeal, was used as the protein source. PBM is a readily available and much less expensive protein by-product of poultry processing. The test diets were fed to fish stocked at commercial rates in ponds and raised to market size (> 1.5 lbs). We used the “ideal protein” approach to formulate typical production diets for HSB. In this approach, amino acids—the building blocks of protein—are added to the diet to match levels found in the fillet of fish. The idea is that levels of amino acids found in the meat will mimic the nutritional requirements of the fish. Two critical amino acids, methionine and lysine, were added to the diets in this way and we also replaced 35%, 70%, and 100% of the fishmeal in the production diets with PBM. The diets also contained other typical ingredients used by fish farmers and were manufactured by a feed mill. HSB were fed as much as they would eat for 600 days. At the end of the trial we found that average fish weight, the percent of fish that were marketable, food conversion, and yield per acre were somewhat lower when fish were fed the diets containing 70% and 100% PBM. Fish fed the 70% and 100% PBM diets also had greater body fat than fish fed the generic diets. The amount of ammonia waste produced by the fish was not different when fed the different test diets. On the other hand, the production performance of fish fed the 35% PBM diet was similar to that of fish fed the typical production diets. These data support our previous results in commercial tanks and demonstrate that poultry by-product can successfully replace a significant portion of fishmeal in commercial HSB diets when critical amino acids are added. These results should reduce the cost of HSB diets.
Technical Abstract: The efficacy of replacing fishmeal with petfood grade poultry by-product (PBM) on an ideal protein basis in commercial diets for hybrid striped bass (HSB) was evaluated under production conditions in pond culture. A generic production diet (GEN) for HSB was formulated to contain 45% protein, 12% lipid and 3.7 kcal/kg. Protein in the generic diet was supplied by a mix of animal and plant sources typically used by the industry that included more than 20% select menhaden fishmeal and less than 10% PBM. A positive control diet (GEN+AA) was formulated by supplementing the generic diet with feed-grade Met and Lys to match the level of those amino acids in HSB muscle at 40% digestible protein. Substitution diets were formulated by replacing 35%, 70%, or 100% of fishmeal in the GEN diet with PBM on a digestible protein basis and then supplementing with Met and Lys (designated 35PBM, 70PBM, and 100PBM, respectively) as needed to maintain concentrations equal to those in the GEN+AA diet. Diet formulation and extrusion were conducted by a commercial mill and all diets met or exceeded known nutritional requirements for HSB. Twenty 0.10-ha ponds (4 ponds/diet) were randomly stocked with juvenile HSB (76 +/- 10g; mean +/-STD) at a density of 7,400/ha and fed for 600 d (Oct 2004 - May 2006). Diets were fed once daily to apparent satiation to a maximum of 95 kg of feed/ha. Total weight and number of fish in each pond were determined at harvest. Weight distributions in each pond were estimated by selecting every 15th fish during harvest. Subsets of ten fish from each of these samples were selected randomly for the determination of body composition and nutrient and energy retention. The availability of indispensable amino acids (IAA) as well as ammonia production from the commercial test diets were determined in separate tank trials. Most production characteristics were not statistically different (P > 0.10) among dietary treatments (Table 1). However, average weight (P = 0.22), percent marketable fish (P = 0.22), food conversion (P = 0.12), and yield per hectare (P = 0.12) were numerically depressed in ponds receiving diets of more than 35% PBM substitution. Size distributions were more peaked (P = 0.05) and somewhat skewed toward smaller fish (P = 0.18) in ponds receiving the 100PBM diet. Fish fed the 70PBM and 100PBM diets had greater (P = 0.001) visceral somatic indices than fish fed the generic diets. Ammonia production in tanks peaked 6-8 hours postprandial when fish were fed at 1.5% of bodyweight and no significant differences among dietary treatments were noted. These data support our previous results in commercial tank trials and further demonstrate the efficacy of poultry by-product meals as a candidate for partial replacement of fish meal in commercial HSB diets on an ideal protein basis.