Effect of diets with different levels of soybean meal and Kemin multi-enzyme on growth performance, body composition, and gut lactic acid bacteria of juvenile Beluga (Huso huso)

In this study, the effects of replacing fish meal with soybean meal on growth performance, feed efficiency, body composition, fatty acid profile and gut lactic acid bacteria of beluga sturgeon, Huso huso. Nine diets were formulated (40% crude protein) in which soybean meal was replaced by fish meal at 0 (control), 40 and 80% supplemented and with three multi-enzyme level 0, 1 or 2 g/kg of Kemin multi-enzyme. Fish were fed on experimental diets for 12 weeks at 1% body weight. Addition of soybean meal decreased growth performance and the effect was more pronounced when with increasing levels of soybean meal (P<0.05) and minimum final weight occurred at 80% of fish meal replaced by soybean meal. Body fatty acid composition was affected by dietary treatments. Fish fed the control diet; diets with enzyme supplementation (without the addition of soybean meal) as well as diets 4 and 5 (40% soybean meal; 0 or 1 g/kg enzyme) had the highest n-3 and eicosapentaenoic acid. In contrast, soybean meal at an inclusion level over 40% negatively influenced n-3 fatty acid. The lowest content of eicosapentaenoic acid and docosahexaenoic acid and n-3 fatty acid was observed in fish fed diets with 80% soybean meal without the inclusion of enzyme (treatment 7). Addition of soybean meal at both 40 and 80% replacement level regardless of enzyme supplementation increased the number of gut Lactococcus lactis, Lactobacillus carvatus, Pediococcus pentaseceous, Lactobacillus plantarum, total aerobic counts and total anaerobic counts. The highest number of bacterial counts occurred in diet containing 80% soybean meal with 2 g/kg enzyme (treatment 9) (P<0.05). The results of this study indicated that soybean meal with enzyme supplementation at 2 g/kg can substitute 40% for fish meal in commercial diets of great sturgeon.