Studies On The Application Of Poultry Oil In The Diet Of Takifugu Rubripes

With juvenile tiger puffer(Takifugu rubripes),the aim of this thesis is to investigate the effects of replacing fish oil(FO)in diet with poultry oil(PO).Firstly,we evaluated the effects of replacing FO in diet with PO on the growth performance,body composition,serum biochemical parameters,fatty acid,lipid metabolism and muscle flavor.On this basis,we investigated the efficacy of the fish oil-finishing strategy in recovering the contents of long-chain polyunsaturated fatty acids in fish body when FO is replaced with PO in the diet.Furthermore,in order to increase the utilization efficiency of PO,we investigated the efficacy of replacing FO with a mixture of poultry oil and coconut oil when replacing fishmeal(FM)with poultry by-product meal(PBM).The following results were observed:1.Fish oil replacement with poultry oil in the diet of tiger puffer(Takifugu rubripes):effects on growth performance,body composition,lipid metabolism,fatty acid,and muscle flavor.Booming fish farming results in relative shortage of fish oil(FO),making it urgent to explore alternative lipid sources.This study comprehensively investigated the efficacy of FO replacement with poultry oil(PO)in diets of tiger puffer(average initial body weight,12.28 g).An 8-week feeding trial was conducted with experimental diets,in which graded levels(0,25,50,75,and100%,named FO,25 PO,50PO,75 PO,and100PO,respectively)of FO were replaced with PO.The feeding trial was conducted in a flow-through seawater system.Each diet was fed to triplicate tanks.The results showed that FO replacement with PO did not significantly affect the growth performance of tiger puffer.FO replacement with PO at 50-100% even slightly increased the growth.PO feeding also had marginal effects on fish body composition,except that it increased the liver moisture content.Dietary PO tended to decrease the serum cholesterol and malondialdehyde content but increase the bile acid content.Increasing levels of dietary PO linearly upregulated the hepatic mRNA expression of the cholesterol biosynthesis enzyme,3-hydroxy-3-methylglutaryl-Co A reductase,whereas high levels of dietary PO significantly upregulated the expression of the critical regulatory enzyme of bile acid biosynthesis,cholesterol 7-alpha-hydroxylase.Dietary PO significantly decreased the muscle LC-PUFA content.Besides,dietary PO also led to changes of volatile flavor compounds in the muscle,such as butanol,pentenal,and hexenal.In conclusion,poultry oil could replace 100% added fish oil in the diet of tiger puffer,without adverse effects on growth and body composition.But the content of LCPUFA and volatile organic compounds was affected.2.Recovery of fatty acid and volatile flavor compound composition in farmed tiger puffer(Takifugu rubripes)with a fish oil-finishing strategyBooming fish farming results in a relative shortage of FO supply,meaning that alternative oils are increasingly used in fish feeds,which leads to reduction of longchain polyunsaturated fatty acids and other relevant changes in fish products.This study investigated the efficacy of an FO-finishing strategy in recovering the muscle quality of farmed tiger puffer.An eight-week feeding trial(growing-out period)was conducted with five experimental diets,in which graded levels(0(control),25,50,75,and 100%)of added FO were replaced by poultry oil(PO).Following the growing-out period was a four-week FO-finishing period,during which fish in all groups were fed the control diet.Dietary PO significantly decreased the muscle LC-PUFA content,whereas in general,the FO-finishing strategy recovered it to a level comparable with that of the group fed FO continuously.The recovery efficiency of EPA was higher than that of DHA.Dietary PO also led to changes of volatile flavor compounds in the muscle,such as butanol,pentenal,and hexenal,whereas the FO-finishing strategy mitigated the changes.In conclusion,the FO-finishing strategy is promising in recovering the LCPUFA and volatile-flavor-compound composition in farmed tiger puffer after the feeding of PO-based diets.3.Effects of fish oil and partial fish meal replacement with 1:1 mixture of poultry oil and coconut oil and poultry by-product meal on growth performance,body composition,fatty acid and muscle flavor of the tiger puffer(Takifugu rubripes)This study comprehensively investigated the efficacy of FO replacement with a1:1 mixture of poultry oil and coconut oil,when partially replacing fishmeal(10% and20%)with poultry by-product meal(PBM)in diets of tiger puffer(average initial body weight,14.29 g).A 45-day feeding trial was conducted with experimental diets,in which graded levels(FO and fish meal,mixture of poultry oil-coconut oil and fish meal,FO and 10% PBM,mixture of poultry oil-coconut oil and 10% PBM,FO and 20%PBM,mixture of poultry oil-coconut oil and 20% PBM;named,FO-FM,PO-FM,FO-5PBM,PO-5PBM,FO-10 PBM and PO-10 PBM,respectively)of FO and FM were replaced.Each diet was fed to triplicate tanks.The results showed that FO replacement with the mixture of poultry oil and coconut oil did not significantly affect the growth performance of tiger puffer.The mixture of poultry oil and coconut oil feeding also had marginal effects on fish body composition,except that it increased the liver moisture content.There was no significant difference in EPA in muscle.The SFA and MUFA highly contained in the mixture of poultry oil and coconut oil were reported to have n-3 LC-PUFA sparing effects.The use of mixture of poultry oil and coconut oil and PBM had effects on the free amino acids of muscle such as histidine,glycine and alanine,but had no significant effects on the muscle texture,water-holding capacity,malondialdehyde content and protein carbonyl content.In serum,there were no significant differences in triglycerides,total cholesterol,total bile acid and protein carbonyl but not in malondialdehyde.The mixture of poultry oil and coconut oil increased the muscle levels of octanal,heptanal,(E)-2-hexenal,pentanol,methyl isobutyl ketone,pentanal,and hexanol,while the PBM increased the muscle levels of methyl isobutyl ketone,pentanal,2-methylbutanal,2,3-pentanedione,methyl acetate,and 2-hexanone.In conclusion,replacing FO with a mixture of poultry oil and coconut oil(1:1)in diet and replacing fish meal with PBM accounting for 20% of diet have no significant effects on the growth performance and body composition of tiger puffer.