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.

Ethanol-soluble components in soybean meal influence the digestive physiology, hepatic and intestinal morphologies, and growth performance of the marine fish pompano (Trachinotus blochii).

This study aimed to examine the effects of ethanol-soluble components (Es) in soybean meal (SBM) on gut content transit, bile acid (BA) and pancreatic digestive enzyme secretions, nutrient apparent digestibility coefficients (ADC), liver and intestinal morphologies, and growth performance of pompano (Trachinotus blochii). The SBM was extracted with aqueous ethanol, then the supernatant and residue were separated and dried to produce ethanol-extracted SBM (ESBM) and the Es. Four experimental diets were formulated with fish meal (FM), ESBM and SBM as main dietary protein sources. The diets were denoted as follows: FMD (FM diet), SBMD (SBM diet), ESBMD (ESBM diet) and ESBM + EsD (ESBM plus Es diet). Thirty-five fingerling pompano with an initial body weight (BW) of 18.3 g were allocated to each of 12 polyvinyl chloride tanks (1000-L holding capacity), resulting in triplicate tanks per dietary treatment. For 10 weeks, the fish were hand-fed the experimental diets to apparent satiation twice daily. The results showed that the final BW, weight gain and specific growth rate were significantly lower, while the feed conversion ratio was higher in the SBMD and ESBM + EsD groups than in the ESBMD and FMD groups (p < 0.05). Fish fed SBMD and ESBM + EsD showed accelerated gastric transit, slowed intestinal mobility, and lowered secretions of BAs and pancreatic digestive enzymes as compared to those fed ESBMD and FMD. Morphological abnormalities in mucosal folds of the posterior intestine, but not the liver, were clearly observed in the SBMD and ESBM + EsD groups. These results indicated that the Es in SBM inhibited the digestive system, leading to decreased nutrient digestibility and growth performance in pompano. The findings of the present study suggested that removal of the Es would effectively improve the nutritional quality of SBM and enhance growth performance of pompano fed a SBM-based diet.