Study On The Effects Of Fly Larvae Pulp On Feeding Attraction,Growth,Nutrition And Immunity Of Monopterus Albus

Rice field eel is a sweet-meated fish with certain medicinal value.It has attracted general attention as one of emerging commercial fishes.In the breeding process,the choice of cost-effective feed is important for improving the economic benefits of breeding rice field eel.Fly larvae,which is rich in in proteins,amino acids,vitamins and antibacterial peptides and other nutrients,is widely used in animal breeding.However,at present,its effects on the growth of rice field eel have few reports.For studying the role of fly larvae in the breeding of rice field eel and then developing new feed,the effects of fresh fly larvae pulp,fly larvae pulp stored for 180 days,frozen fly larvae pulp and Yu Kang Tai I(a fly larvae pulp-based product containing 59.2% fly larvae and 13.2% sugars)and their respective concentrations on the feeding attractant activity,growth,muscle nutrition composition and immune function of rice field eel were studied,with the relative content of mixed feed fixed at 50% and silver carp plasma as a reference.Firstly,the effects of type and relative content of fly larvae pulp on the feeding attractant activity of rice field eel were studied.Fresh fly larvae pulp,fly larvae pulp stored for 180 days,frozen fly larvae pulp and Yu Kang Tai I were used to partially replace silver carp plasma.Then,the new mixed feed were made of fly larvae pulp,silver carp plasma and old mixed feed,in which the relative contents of fly larvae pulp were 5%,10%,15%,20%,25% and 30%.The new feed was used to breed rice field eel for 3 hours and then the original mass and the residual mass were analyzed.Hobby degree was defined to characterize the feeding attractant activity of rice field eel.The results show that fresh fly larvae pulp,frozen fly larvae pulp and Yu Kang Tai I led to better feeding attractant activity than silver carp plasma.In addition,feeding attractant activity increased as the relative contents of fly larvae pulp increased.Secondly,the effects of type and relative content of fly larvae pulp on the growth and muscle nutrition composition of rice field eel were studied.Rice field eels were bred with the above new mixed feed for 90 days.Then,their weight gain rate,survival rate and specific growth rate were used to characterize the growth of rice field eel.Feed coefficient was used to characterize the utilization rate of the new mixed feed.The relative contents of water,proteins,fats,ash contents and non-nitrogen extracts were used to characterize the muscle nutrition composition.The results show that the type and relative content of fly larvae pulp had significant effects on weight gain rate,survival rate,specific growth rate and feed coefficient.When the relative content of fly larvae pulp were fixed at 20%,fresh fly larvae pulp significantly improved weight gain rate,survival rate and specific growth rate and reduced feed coefficient,compared to the reference.The effects of frozen fly larvae pulp and Yu Kang Tai I were worse than those of fresh fly larvae pulp while the effects of fly larvae pulp stored for 180 days were the worst.The increase in relative content of fly larvae pulp reduced the relative content of fats but increased the relative content of ash contents.It had no significant effects on the relative contents of water,proteins and non-nitrogen extracts.The type of fly larvae pulp had no significant effects on the muscle nutrition composition of rice field eel.Thirdly,the blood of rice field eel after 90 days' breeding were sampled to analyze the phagocytic percentage of hemameba,lysozyme activity,concentrations of C3 complements and C4 complements and relative immune protective rate.Then,the effects of type and relative content of fly larvae pulp on immune function of rice field eel were studied.The results show that the type and relative content of fly larvae pulp had significant effects on immune function of rice field eel.When the relative content of fly larvae pulp were fixed at 20%,fresh fly larvae pulp significantly improved the immune function of rice field eel,compared to the reference.The improvement by frozen fly larvae pulp and Yu Kang Tai I were worse while the improvement by fly larvae pulp stored for 180 days were the worst.