Digested soybean protein and taurine influence bile acid level, lipase activity, lipid digestibility, and growth performance of pompano (Trachinotus blochii).

This study aimed to examine the effects of dietary digested soybean protein (DSP) and taurine on bile acid (BA) level, lipase activity, lipid apparent digestibility coefficient (ADC), and growth performance of pompano (Trachinotus blochii). Five diets were formulated with fish meal (FM), defatted soybean meal (SBM), and the DSP as main dietary protein sources. The diets were denoted as follows: FMD (FM-based diet), SBMD (SBM-based diet), SBM+TD (SBM-based diet plus taurine), DSPD (DSP-based diet), and DSP+TD (DSP-based diet plus taurine). Fingerling pompano with an initial body weight (BW) of 21.4 g were stocked in 500-L tanks, with triplicate tanks per dietary treatment. For 8 weeks, the fish were hand-fed the experimental diets to apparent satiation twice daily. The results showed that the DSPD and DSP+TD groups had significantly higher final BW, weight gain, and specific growth rate, but lower feed conversion ratio, than the SBMD and SBM+TD groups, respectively (P < 0.05). There were no significant differences in growth and feed performances between fish fed DSP+TD and FMD. The gallbladder and anterior intestinal BA levels, anterior intestinal lipase activity, and lipid and protein ADCs were markedly increased in fish fed DSPD and DSP+TD compared to those fed SBMD (P < 0.05), and no significant differences were detected between the DSP+TD and FMD groups. The findings of the present study suggested that dietary DSP inclusion with taurine supplementation might effectively improve lipid digestion and this contributed to growth enhancement in pompano fed a soybean protein-based diet.

Dietary replacement of fish meal by defatted and fermented soybean meals with taurine supplementation for pompano fish: effects on growth performance, nutrient digestibility, and biological parameters in a long-term feeding period.

A 16-wk growth trial was conducted to examine the effects of dietary replacement of fish meal by defatted soybean meal (SBM) and fermented soybean meal (FSBM) with taurine supplementation on growth performance, nutrient apparent digestibility coefficient (ADC) and biological parameters of pompano fish. The FSBM was produced by fermenting SBM with Lactobacillus spp. Seven isonitrogenous and isoenergetic diets were formulated to replace 35% or 50% of fish meal by SBM or FSBM with taurine supplementation. The diets are denoted as follows: FM, SBM35, SBM35T, FSBM35T, SBM50, SBM50T, and FSBM50T. The FM (the basal diet) contained fish meal as a main source of dietary protein. Taurine was supplemented to SBM35T, FSBM35T, SBM50T, and FSBM50T at the level of 15 g/kg diet. Pompano juveniles with an initial body weight (BW) of 80 g reared in floating net cages were fed the experimental diets twice daily for 16 wk. Results showed that the final BW, weight gain, and feed conversion ratio of fish fed SBM35 and SBM50 were significantly lower than those of fish fed FM (P < 0.05), indicating that the replacement of fish meal by SBM at the rate of 35% in the diet is excessive for pompano. Supplementation of taurine to the SBM-included diets significantly increased growth performance and feed utilization (P < 0.05); however, these diets did not restore the performance back to a level equivalent to that of fish offered the basal diet. Meanwhile, fish fed FSBM35T had comparable growth and feed performances to those fed FM. Hematocrit values, total biliary bile acid levels, whole body lipid contents, and tissue taurine concentrations of fish fed SBM35 and SBM50 were the lowest among the treatments, but these parameters were improved by taurine supplementation and FSBM inclusion in the diet. Taurine supplementation increased lipid ADC, and SBM fermentation slightly enhanced both lipid and protein ADCs of the fish. These findings suggest that the combination of FSBM and taurine supplementation is an effective way to improve growth performance, nutrient digestibility, and biological parameters, and that FSBM with taurine supplementation can replace 35% of fish meal in pompano diets without any negative effects on growth and feed performances in a long-term feeding period.