Effect of dietary taurine supplementation on growth performance and bile salt activated lipase activity of common dentex, Dentex dentex, fed a fish meal/soy protein concentrate-based diet

Common dentex were fed three isoprotein and isoenergetic diets to investigate the effect of partial substitution of fish meal by soy protein concentrate (0 [FM], 25 [SM25] and 40% [SM40]) in the presence or absence of taurine (T) supplementation (2 g kg− 1 on a dry weight basis) [FM + T], [SM25 + T] and [SM40 + T], on growth related parameters, muscle composition and bile salt activated lipase activity. The fish were fed twice a day by hand to apparent satiation over the course of a 12-week growth trial.The [SM40] diet resulted in lower feed intake compared to the [FM] and [SM25] diets, lower specific growth rate compared to the [FM] diet, lower condition factor and increased mortality of dentex compared to the [FM] and [SM25] diets. On the other hand, the [SM25] diet had no adverse effect on either feed intake or specific growth rate of dentex compared to the [FM] diet. The hepatosomatic and mesenteric fat indices did not change by increasing soy content. Moreover, no difference was observed in the composition of muscle in dentex fed different proportions of soy protein concentrate. However, the activity of the bile salt-activated lipase in liver was significantly lower in fish fed the [SM25] diet than in fish fed the [FM] diet.Dietary taurine supplementation increased the specific growth rate and daily feed intake while it reduced feed conversion ratio of dentex. Comparison among groups showed that dietary taurine supplementation increased feed intake but not specific growth rate in the [SM40 + T] group compared to [SM40] group. The condition factor was higher in fish fed the [FM] diet compared to the [SM25 + T] and [SM40 + T] diets. However, no difference was observed between the [SM25] and [SM40] groups compared with the [SM25 + T] and [SM40 + T] groups, respectively. Analysis of the chemical composition of the muscle showed that the [SM25 + T] fed fish had higher crude protein compared to the [SM40 + T] fed fish. Furthermore, the mesenteric lipid index was higher in [SM25 + T] fed fish compared to those fed the [SM25] and [SM40 + T] diets. The activity of the bile salt-activated lipase in the liver increased in fish fed the three diets [FM], [SM25] and [SM40] in the presence of taurine, indicating that taurine in diets at 2 g kg− 1 may improve lipid metabolism, although no significant differences were observed in the total fat content of the muscle of fish fed either of these experimental diets.In conclusion, it appears that in dentex, partial substitution of fish meal is possible with 25% of soy protein concentrate without affecting growth, which can be improved further by dietary taurine supplementation of 2 g kg− 1 diet.