Taurine supplementation in high-soy diets affects fillet quality of European sea bass (Dicentrarchus labrax)

This study evaluated the effects of taurine supplementation to diets containing a high dietary inclusion of soybean meal and soy protein concentrate on growth performance and fillet quality of juvenile European sea bass (Dicentrarchus labrax). A control diet (C+) was produced containing high levels of fishmeal (30% FM) and soybean meal (20% SBM). Three other experimental diets were prepared to contain a lower FM inclusion (25%), and a higher amount of soy products (20% of SBM plus 12% soy protein concentrate, SPC) supplemented with three graded levels of crystalline taurine, 0.2%, 0.5% and 1.0% (T0.2, T0.5 and T1.0), respectively. A fifth diet was also prepared having a similar composition as the latter three diets but without the addition of crystalline taurine (negative control diet, C-). All diets were iso-nitrogenous (44%), iso-lipidic (20%) and iso-energetic (22 MJ kg(-1)) and were fed to five triplicate groups of sea bass (initial weight 86 g) over the course of a 12-week trial. Dietary taurine supplementation did not affect the growth performance and feed efficiency (P > 0.05). Proximate composition of whole body and muscle were similar among groups (P > 0.05). Taurine dietary supplementation had no effect on the level of intraperitoneal fat deposition (P > 0.05). However, muscle taurine concentration was found to increase gradually in sea bass fed the elevated levels of taurine (P < 0.05). Interestingly, the hardness and chewiness of the fillet, recorded by texture analysis, increased significantly at higher dietary taurine levels (P < 0.05). The highest adhesiveness values were obtained in sea bass fed the C-diet, whereas the lowest ones were found in fish fed the T1.0 diet (P < 0.05). No significant (P > 0.05) impact of diets on texture fillet springiness and cohesiveness was found (P > 0.05). In general, no significant differences were observed by the test panel, however, fish fed the diet supplemented with 1.0% taurine exhibited lower fillet elasticity, thus indicating a potential textural difference in accordance with those obtained from the texture analysis of fish muscles. The histological analysis did not indicate any differences in the gut and liver of the fish fed the experimental diets. Overall, the findings of the present study showed that 1.0% taurine supplementation in diets incorporating high levels of soy products might have a pronounced effect on flesh quality of European sea bass.