The effects of replacing dietary fishmeal by soybean meal with taurine supplementation on feed intake, growth, feed utilization, body composition and waste output of largemouth bass were examined. A control diet (C) contained 400 g/kg fishmeal, 20%, 40% and 60% of fishmeal in diet C was replaced by soybean meal, with or without 5 g/kg taurine supplementation (abbreviated as S20 + T, S40 + T, S60 + T, S20, S40 and S60, respectively). Significantly lower weight gain was found in fish fed diet S60 compared with fish fed diet C (p < 0.05), while no significant difference was found in weight gain between fish fed diet C and fish fed diets S20, S20 + T, S40 + T and S60 + T (p > 0.05). No statistically differences were found in feed intake and feed conversion ratio between fish fed diet C and fish fed diets S20, S20 + T, S40, S40 + T and S60 + T (p > 0.05). No significant differences were found in nitrogen retention efficiency, body crude protein content and nitrogen waste among fish fed different test diets (p > 0.05). This study suggests that dietary fishmeal level for largemouth bass can be reduced to 240 g/kg and further reduced to 160 g/kg with taurine addition, with soybean meal used as a fishmeal substitute.

An eight‐week feeding trial was conducted to evaluate the feed intake, growth, feed utilization, body composition and waste output of juvenile hybrid bream at different feeding frequencies (0.5, 1, 2, 3 or 4 meals/day). Fish (initial body weight of 10.6 ± 0.8 g) were fed to satiation at each feeding. The test diet contained 336 g/kg crude protein and 79 g/kg crude lipid. The weight gain significantly increased with increase in feeding frequency from 0.5 to 3 meals/day (p < 0.05) and afterwards did not change with feeding frequency from 3 to 4 meals/day (p > 0.05). The feed intake increased with increase in feeding frequency (p < 0.05). Fish fed at 3 meals/day exhibited the lowest feed conversion ratio and waste output of nitrogen and phosphorus, however, the highest nitrogen retention efficiency (p < 0.05). No significant differences were found in the phosphorus retention efficiency, the body composition of crude protein, ash and phosphorus among all the feeding frequencies (p > 0.05). The body lipid content increased, whereas the content of moisture decreased, with the increase in feeding frequency (p < 0.05). The present study reveals that the optimum feeding frequency is 3 meals/day for hybrid bream.

The present study was conducted to examine the effects of taurine supplementation on feed intake, growth, feed utilization, body composition, waste output, hepatic antioxidant enzymes, and intestinal microflora of Largemouth Bass Micropterus salmoides that were fed a low fish meal diet. Three isoproteic (49% crude protein) and isolipidic (9.5% crude lipid) diets were formulated: one diet contained 40% fish meal and served as the control (FM diet), and 60% of the fish meal in the FM diet was replaced by soybean meal either without taurine supplementation (SBM diet) or with 0.5% taurine supplementation (SBM+T diet). Lower feed intake, final body weight, weight gain, condition factor, and hepatosomatic index and a higher feed conversion ratio (FCR) were found in fish that received the SBM diet compared to fish that were fed the FM diet, but no significant difference was found in feed intake, final body weight, weight gain, FCR, condition factor, or hepatosomatic index between fish in the FM and SBM+T diet groups. No significant differences were found in nitrogen retention efficiency, body composition, nitrogen waste, or activities of total antioxidant capacity, superoxide dismutase, and glutathione peroxidase among fish fed the different test diets, and the alpha diversity of intestinal microbiota also did not differ among diet groups. The abundance of Proteobacteria and Firmicutes increased while the abundance of Fusobacteria decreased in the SBM diet group relative to the FM diet group; in contrast, dietary taurine (SBM+T diet) restored the abundance of Proteobacteria to a level similar to that in fish receiving the FM diet. This study suggests that the dietary fish meal level for Largemouth Bass can be reduced from 40% to 16% if soybean meal is used as an alternative protein with 0.5% taurine supplementation.Fish meal is characterized by high prices and finite resources, and replacement of fish meal with alternative protein sources promotes the development of fish aquaculture toward a sustainable orientation (Naylor et al. 2009). Soybean meal has attracted constant attention due to its high protein digestibility, huge global production, and reasonable market price (Hardy 2010). It has been demonstrated that dietary fish meal can be partly replaced by soybean meal in some carnivorous fish species like Japanese Seabass Lateolabrax japonicus (Zhang et al. 2018), European Bass Dicentrarchus labrax (Bonvini et al. 2018), Rainbow Trout Oncorhynchus mykiss (Yes ¸ilayer and Kaymak 2020), Largemouth Bass Micropterus salmoides (Li et al. 2021b), and Spotted Seabass Lateolabrax

An 8-week feeding trial was conducted to investigate the effects of different dietary selenium yeast levels on growth, nutrient retention, waste output, and antioxidant capacity of juvenile triangular bream (Megalobrama terminalis). Five isonitrogenous (320 g/kg crude protein) and isolipidic (65 g/kg crude lipid) diets were formulated, with supplementation of graded levels of selenium yeast at 0 (diet Se0), 1 (diet Se1), 3 (diet Se3), 9 (diet Se9), and 12 g/kg (diet Se12). No significant differences were found in initial body weight, condition factor, visceral somatic index, hepatosomatic index, and whole body contents of crude protein, ash, and phosphorus among fish fed different test diet. The highest final body weight and weight gain rate were found in fish fed diet Se3. The specific growth rate (SGR) is closely related to dietary selenium (Se) concentrations with a relationship described as SGR = – 0.0043   S e 2 + 0.1062   Se + 2.661 . Higher feed conversion ratio was found, while lower retention efficiencies of nitrogen and phosphorus were found in fish fed diets Se1, Se3, and Se9 than in fish fed diet Se12. Contents of selenium in whole body, vertebra, and dorsal muscle increased with dietary supplementation of selenium yeast increased from 1 mg/kg to 9 mg/kg. Lower nitrogen and phosphorous waste was found in fish fed diets Se0, Se1, Se3, and Se9 than in fish fed diet Se12. Fish fed diet Se3 exhibited the highest activities of superoxide dismutase, glutathione peroxidase, and lysozyme while the lowest malonaldehyde content in both the liver and kidney. Our results showed that the optimal dietary selenium requirement for triangular bream should be 12.34 mg/kg based on the nonlinear regression on SGR, and fish fed diet Se3 in which selenium concentration (8.24 mg/kg) was close to the optimal requirement displayed the best growth performance, feed nutrient utilization, and antioxidant capacity.