Growth, nutrient retention, innate immune response, and intestinal morphology of juvenile, soy-naïve hybrid striped bass, Morone saxatilis x M. chrysops, fed commercial-type, soy-based, fish meal replacement diets

Authors: RAMENA, YAHTISH - University Of Arkansas At Pine Bluff; Rawles, Steven - Steve; LOCHMANN, REBECCA - University Of Arkansas At Pine Bluff; Gaylord, Thomas; McEntire, Matthew - Matt; Farmer, Bradley; BAUMGARTNER, WES - Mississippi State University; Webster, Carl; Beck, Benjamin; Green, Bartholomew - Bart; Barnett, Louis - Matt

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2020
Publication Date: 2/22/2020
Citation: Ramena, Y., Rawles, S.D., Lochmann, R., Gaylord, T.G., Mcentire, M.E., Farmer, B.D., Baumgartner, W., Webster, C.D., Beck, B.H., Green, B.W., Barnett, L.M. 2020. Growth, nutrient retention, innate immune response, and intestinal morphology of juvenile, soy-naïve hybrid striped bass, Morone saxatilis x M. chrysops, fed commercial-type, soy-based, fish meal replacement diets. Aquaculture. https://doi.org/10.1016/j.aquaculture.2020.735150.
DOI: https://doi.org/10.1016/j.aquaculture.2020.735150

Interpretive Summary: Hybrid striped bass were fed diets in which fish meal was replaced by six different soy products, including three non-genetically modified (non-GM) soybean meals that were bred for high protein content and potentially lower anti-nutritional factors (ANFs). ANFs are compounds found in many plant ingredients that can cause intestinal health issues, like enteritis. Gut enteritis reduces the digestion and absorption of nutrients from food in some animals. Soy induced enteritis is a particularly well-known phenomenon negatively affecting many land and aquatic based farm animals, especially trout and salmon (salmonids). We first determined the nutrient and energy digestibility in the soy products of interest that included the three non-GM soybean meals, the parent soybean variety (Ozark) of the three non-GM varieties, a well-characterized, conventional soybean meal from the industry (Archer Daniels Midland; ADM), a soy protein concentrate (SPC), and, as a control, Special-Select® menhaden fish meal (MFM-S), which is a high quality grade of fish meal. A fish meal replacement trial was then conducted in which MFM-S was included at 25.5% of a control diet and then sequentially replaced by each of the above soy products using the latest animal diet formulation philosophy (ideal protein theory). All fish used in the fish meal replacement study were small and soy-naïve, that is they were obtained as sac fry (not yet eating) and then transitioned to soy-free diets prior to the study in order to create juvenile fish that were potentially the most sensitive to soy-induced performance issues. Fish (about 4 g in initial weight) were fed to satiation twice daily for 73 days in a flow-through freshwater culture system to about 50-60 g (2-2.5 oz each) final weight. Average daily feed intake did not differ significantly among the test diets, but fish fed the conventional soybean (ADM) diet were larger than those fed the fish meal control. Otherwise, final weight and weight gain for fish fed all other soy-based diets were not different from the control. Gains in fish fed the soy protein concentrate (SPC) diet fell below those of fish fed some of the other soybean meals. Larger livers were also observed in fish fed the SPC diet, which indicates some issue with dietary nutrient balance or utilization by the animal. Generally, however, liver size as a result of dietary soy inclusion did not differ from the fish meal control group. Feed conversion ratio (FCR) was slightly poorer for fish fed the R05-1772 non-GM soybean based diet compared to those fed the control, but otherwise FCR did not differ among diets. Protein, energy and amino acid retention from the diets also did not differ among the test diets. Final fillet ratio and whole body nutrient composition did not differ among diets. There were slight differences in whole body energy, moisture and ash without apparent trends among dietary treatments. Hematological (blood) indicators of fish immune status also did not differ significantly among diets. Survival after challenge with a bacterial disease was shortest in groups of fish that had been fed the fish meal control or conventional soybean meal (ADM) diets, whereas fish that had been fed the Ozark and R05-1772 non-GM soy based diets had significantly longer likelihood of survival. After 73 days of feeding, measurements taken on cross-sections of the intestines indicated moderate intestinal inflammation in fish fed some of the soy-based diets; however, these signs virtually disappeared when intestinal samples were checked in fish that were fed the test diets for an additional 5 months. These data suggest that complete replacement of fish meal with various soybean meals is possible in hybrid striped bass using ideal protein diet formulas. Moreover, hybrid striped bass appear to adapt well to fish meal-free, soy-based diets over the long run and are m

Technical Abstract: In continuing efforts to develop high-performing, plant-based commercial diets for hybrid striped bass, Morone chrysops × M. saxatilis, nutrient, energy and amino acid (AA) availabilities in six soy products were determined and used to formulate and evaluate commercial type, ideal protein, fish meal (FM) replacement diets that were fed to soy-naïve, juvenile (3.72 ± 0.01g initial weight) hybrid striped bass (HSB) for up to 5 months. The six soy products tested were soy protein concentrate (SPC; Profine VF™), a conventional soybean meal (SBM) from Archer Daniels Midland (ADM), three non-genetically modified (non-GM) soybean varieties from the University of Arkansas (R05-1415, R05-1772, and R07-2001) with high protein content and putatively reduced anti-nutritional factors (ANFs), and Ozark soybeans—another commercial variety and parent to the three non-GM strains used in this study. Fish performance was evaluated in terms of growth, composition of growth, dietary nutrient retention, innate immune status, and resistance to bacterial disease challenge after 73 d of feeding, as well as intestinal morphology after 73 d and 5 months of feeding the test diets. The control diet included Special-Select® menhaden fish meal (MFM S; Omega Protein) at 25.5% of diet and contained 40% digestible protein (DP) and 16% lipid from a constant ratio of fish: poultry: soy oil. MFM-S was then replaced by each of the soy products of interest on a digestible protein basis and supplemented with Met, Lys, and Thr based on 40% HSB muscle AA profile. Fish used in the FM replacement trial were obtained as sac fry and reared to juveniles on soy-free diets in order to create fish that were potentially most sensitive to soy-induced performance issues. Fish were fed to satiation twice daily in a flow-through freshwater culture system. Average daily intake (ADI) did not differ significantly (P > 0.05) among treatments (2.2-2.5% of body weight/day). Fish fed the ADM diet were larger (58.2g) and gained more (1465%) than those fed the FM control (50.5g, 1251%); otherwise final weights (46.6-54.3g) and weight gains (1153%-1355%) for fish fed all other soy-based diets did not differ from the control. Gains in fish fed the SPC diet fell below those of fish fed the ADM, Ozark, and R0-1415 diets. Conversely, the largest livers were observed in fish fed the SPC diet (2.2%, HSI – hepatosomatic index) which were larger than those observed in fish fed the ADM (1.8%), R0-1415 (1.9%) and Ozark (1.6%) diets. However, liver size as a result of dietary soy inclusion generally did not differ from the FM control (2.0%). Feed conversion ratio was slightly poorer for fish fed the R05-1772 diet (1.09) compared to those fed the control (0.93); otherwise FCR did not differ among diets (0.97-1.01). Protein (35.7-40.9%), energy (39.0-43.2%) and AA retention efficiencies did not differ among treatments. Final muscle ratio, whole body protein, amino acids, and lipid were not different among treatments. There were slight differences in whole body energy, dry matter and ash without trends among treatments. Hematological and innate immune parameters did not differ significantly among treatments. Time to death after challenge with Flavobacterium columnare was shortest in fish that had been fed the FM control (1.13 d) or ADM (1.50 d) diets; whereas, fish that had been fed the SPC (2.57 d), Ozark (3.10 d), and R05-1772 (3.90 d) diets had significantly longer likelihood of survival than fish fed the FM control or ADM diets. Intermediate but overlapping survival was observed in fish fed the R05-1415 (2.27 d), and R07-2001 (2.30 d) diets. After 73 days of feeding, measures of distal gut morphology did not differ significantly among dietary treatments; whereas, indications of moderate intestinal inflammation were noted in proximal intestinal morphology between fish fed the soy-bas