Effects of Bacillus licheniformis on the growth performance,muscle quality and earthy odor control of grass carp（Ctenopharyngodon idellus）

【Objective】 To investigate the effects of Bacillus licheniformis on the growth performance, muscle quality and earthy odor control of grass carp（Ctenopharyngodon idellus）, which could provide reference for the prevention and control of earthy odor in cultured C. idellus and the improvement of muscle quality. 【Method】 A total of 360 C. idellus（with an initial weight of 25.00±1.50 g） were randomly divided into 4 groups: T1（fed with basic diet）, T2（fed with B. licheniformis diet）, T3（fed with basic diet adding Streptomyces thermocarboxydus and S. cyaneofuscatus）, T4（fed with B. licheniformis diet adding S. thermocarboxydus and S. cyaneofuscatus）. After a 30 d feeding trial, the effects of B. licheniformis on grass carp growth performance, muscle texture characteristics, muscle conventional nutrient content, muscle fatty acid content and earthy odor substance concentration were detected.【Result】The addition of B. licheniformis could effectively improve the growth performance and muscle texture characteristics of C. idellus. Compared with the T1 group, the weight gain rate and specific growth rate of the T2 group were significantly increased（P＜0.05, the same below）. The muscle hardness of the T2 and T4 groups was significantly greater than that of the T1 and T3 groups. The addition of B. licheniformis to feed could effectively enhance the muscle quality of C. idellus. The crude protein content and total polyunsaturated fatty acid content in the muscles of the T2 and T4 groups were significantly higher than those of the T1 and T3 groups respectively, and the contents of docosahexaenoic acid, eicosapentaenoic acid and arachidonic acid were all significantly higher than those of the T3 group. The addition of B. licheniformis to feed could effectively reduce the earthy odor substance concentration in C. idellus muscle, with group T2 showing significantly lower geosmin（GSM） concentration than T1, T3 and T4 groups. The 2-methylisoborneol（2-MIB） concentration in group T3 was significantly higher than in T1, T2 and T4 groups. Correlation analysis results indicated that the concentrations of GSM and 2-MIB were both negatively correlated with the total content of polyunsaturated fatty acids, and the concentration of GSM was significantly and positively correlated with the crude fat content. 【Conclusion】 Adding B. licheniformis to the basic diet can enhance the growth performance of C. idellus, optimize muscle nutritional composition, improve texture characteristics and reduce earthy odor substance accumulation in muscle. B. licheniformis may reduce the accumulation of earthy odor substance in C. idellus muscle by regulating fatty acid metabolism.