Effects of Dietary Replacement of Fish Meal by Raw and Fermented Soybean Residues on Growth Performance, Biological Parameters and Nutrient Digestibility in Red Tilapia Fish (Oreochromis sp.)
Effects of Dietary Replacement of Fish Meal by Raw and Fermented Soybean Residues on Growth Performance, Biological Parameters and Nutrient Digestibility in Red Tilapia Fish (Oreochromis sp.)
Hung Phuc Nguyen1*, Doan Van Thuoc2*, Nguyen Thi Trung Thu1, Huong Tran Thi Mai3, Nguyen Tran Khanh Hoa1, Nguyen Thi Tuyet Nhi1, Nguyen Phuong Thao1, Tran Thi Loan2 and Nguyen Thi Huyen My2
ABSTRACT
This study was conducted to examine the effects of dietary replacement of fish meal (FM) by raw soybean residue (SR) and fermented soybean residue (FSR) on growth performance, biological parameters and nutrient apparent digestibility coefficients (ADCs) of red tilapia (Oreochromis sp.). FSR was obtained by fermenting SR with Bacillus subtilis V37. Five isonitrogenous and isoenergetic diets were formulated to replace 35% or 50% of FM by SR or FSR. The diets were denoted as follows: FMD, SR35D, FSR35D, SR50D, and FSR50D. The FMD (the reference diet) contained FM as a main source of dietary protein. A total of 300 fingerling red tilapia with an initial body weight (BW) of 13.7 g were randomly distributed into 15 tanks (20 fish/tank, 3 tanks/dietary treatment) and fed the experimental diets twice daily, for 8 weeks. Results showed that fish fed SR35D and SR50D had significantly lower final BW, weight gain (WG) and specific growth rate (SGR), but higher feed conversion ratio (FCR), than fish fed FMD (P < 0.05). Meanwhile, no significant differences in growth performance and feed utilization between the FSR35D and FMD groups were detected. Fish fed FSR-included diets showed significantly better growth performance and FCR than those fed SR-included diets (P < 0.05). Feeding the fish with SR35D and SR50D reduced digestive enzyme activity, bile juice secretion, and nutrient ADCs. These parameters of the experimental fish were markedly improved by feeding with FSR35D and FSR50D, and no statistical differences were observed between FSR35D- and FMD-fed fish. The results of the current study indicated that SR interfered with digestive enzyme activity, bile juice secretion, nutrient ADCs, and growth and feed performances. The enhancements of these parameters in fish fed FSR-included diets suggested that fermentation of SR with Bacillus subtilis V37 benefited digestive physiology, growth performance and feed utilization of red tilapia fed soybean protein-based diets.
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