Effects of Taurine Supplementation on Growth, Feed Utilization, Antioxidant Capacity, and Intestinal Microflora of Largemouth Bass Fed a Low Fish Meal Diet

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.