Effects Of Dietary Cottonseed Protein Concentrate And Selenium Yeast On Growth Performance,Health Status And Flesh Quality Of Grass Carp,Ctenopharyngodon Idellus

Soybean meal is one of the main protein raw materials in aquatic feed.At present,soybean in China mainly depends on import,so it is urgent to find alternative protein source to meet the demand of aquatic industry.Cottonseed protein concentrate(CPC)is a product obtained from common cottonseed meal through low-temperature leaching and double solvent extraction.The content of free gossypol is low.It has a protein content of over 60%,a balanced amino acid composition,and high levels of arginine and glutamate.A large number of studies have proved that it has a good effect of replacing fish meal in aquatic feed.Taking grass carp as the research object,the study evaluated the effects of CPC replacing soybean meal on growth performance,health status and flesh quality of experimental fish,and the effect of adding yeast selenium on the basis of complete substitution,in order to provide basic data for the substitution of soybean meal and the utilization of CPC.Trial 1 The effects of CPC replacing soybean meal on growth performance,flesh quality and health status of grass carp.Six kinds of isonitrogenous and isolipidemic diets were designed.CPC was used to replace 0%(C0),15%(C15),30%(C30),45%(C45),75%(C75)and 100%(C100)soybean meal in grass carp diets,and fed to grass carp(502.46 ± 0.40 g)in pond cages for 90 days.The results showed that:(1)In terms of growth and physical indicators,there were no significant differences in feed conversion ratio or specific growth rate among groups(P>0.05),the viscerasomatic index of C45 group was significantly higher than that fed C0 diet(P<0.05).(2)In terms of health status,there were no pathological changes in liver and muscle tissue of grass carp in all groups.The plasma albumin and globulin ratio of C100 group was significantly lower than that fed C0 diet(P<0.05),the plasma superoxide dismutase activity of C15 group was significantly higher(P<0.05).(3)In terms of flesh quality,the crude protein content of grass carp muscle in C75 group and the isoleucine content of grass carp muscle in C30 group were significantly higher than those fed the C0 diet(P<0.05);Compared with C0 group,the muscle springiness and adhesiveness of grass carp in the C30,C45 and C100 groups were significantly higher(P<0.05),the sarcomere lengths of C75 and C100 groups were significantly higher(P<0.05).The results showed that CPC completely replaced soybean meal in grass carp diet didn’t affect growth performance,and could improve its immunity and flesh quality.Trial 2 The effects of selenium yeast(SY)supplementation on growth performance,health status and flesh quality of grass carp in a practical diet replacing soybean meal with CPC.Four isonitrogenous and isolipid diets were prepared,in which 0mg/kg(SY0),0.3mg/kg(SY3),0.6mg/kg(SY6)and 0.9mg/kg(SY9)SY were added on the basis of CPC replacing soybean meal,respectively,and fed to grass carp(309.74±0.33 g)in pond cages for 54 days.The results showed that:(1)In terms of growth and physical indicators,growth performance of SY3 and SY6 groups were not significantly affected compared with SY0group(P>0.05),but the weight,specific growth rate and weight gain rate of SY9 group were significantly lower than those fed SY0 diet(P<0.05).The intestine index of SY3 group was significantly lower than that fed SY0 diet(P<0.05);(2)In terms of health status,the hepatosomatic index(HSI)decreased significantly and the health status improved in SY3 and SY6 groups.The morphology of muscle tissue supplemented with SY was normal,and the muscle fibers were separated from the intima;(3)In terms of flesh quality,compared with the SY0 group,the crude protein content,selenium content and hardness of SY3 group were significantly increased(P<0.05),and the cohesiveness was significantly decreased(P<0.05).The study indicated that adding 0.3mg/kg SY in the practical diet completely replacing soybean meal with CPC could improve health status and flesh quality of grass carp.In conclusion,it is considered that the use of 18.27% CPC in grass carp diet doesn’t affect growth performance,but can improve the health status and flesh quality of grass carp,and can completely replace soybean meal.On this basis,the addition of SY(dietary selenium content: 0.6 mg/kg)can improve health status of grass carp,improve crude protein content,selenium content and hardness of muscle,and improve flesh quality.