Effects of soybean meal replacement with added taurine in fish meal diets for summer flounder (Paralichthys dentatus)
Aquaculture feed costs can be reduced if fish meal (FM) is substituted, either partially or completely with plant proteins. Previous experiments have shown that (a) soybean meal (SBM) alone could not replace FM in diets for cultured juvenile summer flounder (Paralichthys dentatus) and there were no growth differences among 20, 30, and 40% SBM replacement of FM, but all were better than 50% SBM replacement, and (b) that 40% (but not 70%) replacement of FM was possible, as long as 1.0% taurine was added to the diet. The current study tested whether higher levels of SBM could be included in FM diets if higher levels of taurine were used. Four SBM replacement levels (40, 50, 60, and 70%), combined with two dietary taurine levels (1.5 and 2.0%) were tested. A FM diet control was also included. Fish were fed for eight weeks and their survival and growth were measured. In addition, fish from three of the treatments (FM, 40/1.5, and 70/1.5) were subsequently subjected to a bacterial challenge with Vibrio harveyi, which is known to cause flounder infectious necrosis enteritis (FINE). Fish were intraperitoneally injected with V. harveyi and their survival was followed for 7 days. Survival and growth data were analyzed by one-way ANOVA and the survival of fish over time in the bacterial challenge was analyzed by SigmaStat log-rank survival analysis. Survival ranged from 92–100% in the various treatments of the feeding trial and was not significantly different among treatments. All of the SBM replacement diets yielded significantly less growth than the FM control. Diets containing 40, 50, 60 and 70% SBM were not significantly different in the growth of fish. Level of taurine addition did not affect the outcome. It was not clear why the 40% replacement diets with taurine did not perform as well as the FM control diets with respect to growth and food conversion ratio (FCR), as in our previous experiments. Results of the bacterial challenge indicated that fish fed the 40/1.5 and 70/1.5 diets had significantly better survival than did fish fed the FM diet. Any ability of SBM properties to confer added disease resistance to FINE would be tremendously beneficial. Cost savings in reduced management and treatment, as well as higher numbers of healthier fish for market are important advantages for success in aquaculture. Our results suggest that summer flounder diets containing 50 to 60% SBM are just as effective as 40% SBM, without significantly hindering growth or survival when amino acids, phytase, and at least 1.5% taurine are supplemented. SBM used in diets may provide immunostimulation to lessen juvenile summer flounder susceptibility to FINE infection.
"Effects of soybean meal replacement with added taurine in fish meal diets for summer flounder (Paralichthys dentatus)"
Dissertations and Master's Theses (Campus Access).