Effects of taurine supplementation in soy-based diets on growth performance and fillet quality in European sea bass (Dicentrarchus labrax)

Abstract

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 improve the growth performance and feed utilization significantly (P < 0.10), however, the dietary treatment with 1.0% taurine supplementation showed a slight improvement in growth and feed efficiency. Body and muscle proximate composition did not differ 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 increasing levels of taurine (P < 0.05). Hardness and chewiness of the fillet, recorded by texture analysis, increased significantly at higher dietary taurine levels (P < 0.05) A slight decrease in fillet adhesiveness occurred, but was not significantly dependent on taurine concentration (P > 0.05). Other texture parameters such as fillet springiness and cohesiveness showed minor changes over dietary treatments (P > 0.05). Although no significant differences were observed by the test panel, there was a tendency of lower elasticity for the fish fed the diet supplemented with 1.0% taurine, 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 obvious differences in the gut and liver of the fish fed the different experimental diets. Overall, the findings of the present study showed that 1.0% taurine supplementation in diets with high levels of soybean products might have a beneficial effect on growth performance and a pronounced effect on flesh quality of European sea bass.