Effects Of Compound Feeds With Different Fat Sources On Growth,Physiological And Biochemical Indexes In GIFT Tilapia Juveniles,Oreochromis Niloticus

At present,in the production of aquatic compound feed,oils are generally added to feed ingredients in liquid form or sprayed onto feed particles in a vacuum environment.However,there were few reports about the application of fat powders in aquaculture.In addition,tilapia compound feed is generally used soybean oil which is rich in linoleic acid as the fat source.But the effects of the linoleic acid / linolenic acid ratio on its growth,physiological and biochemical indexes in feeds are rarely studied.In this study,soybean oil(linoleic acid: linolenic acid = 9: 1)and a blend oil composed of soybean oil and rapeseed oil(linoleic acid: linolenic acid = 5: 1)were used as oil sources.With soybean oil and blend oil as fat sources,six diets were formulated and named as: soybean oil(D1),soybean oil powder(D2),soybean oil powder with emulsifier(D3),blend oil(D4),blend oil with emulsifier(D5),blend oil powder with emulsifier(D6).Each diet was fed to triplicate groups of GIFT tilapia juveniles Oreochromis niloticus(initial average weight 15.38g)in an indoor aquarium for 8weeks to evaluate the effects of the form of the fat source,fatty acid composition(linoleic acid/linolenic acid ratio)and emulsifier treatment on the effect of feed application.The main results and conclusions obtained are as follows:1.Growth performance and proximate composition indexes: There were no significant differences in weight gain rate,specific growth rate,survival rate,feed coefficient,HSI,whole fish crude ash,muscle crude protein and muscle crude lipid among the D1-D6groups(P>0.05).Between different fat source morphology treatment groups,the moisture and ash of whole fish and muscle in D3 groups were significantly lower than D1 group(P<0.05).The crude lipid of whole fish in D6 group was significantly lower than D4 group(P<0.05).Between different linoleic acid / linolenic acid ratio treatment groups,the whole fish dry matter in the D4 groups was significantly lower than the dry matter of D1 group(P<0.05),the whole fish crude protein content and muscle crude ash in the D4 groups were significantly higher than the whole fish crude protein content of D1 group(P<0.05).Between the emulsifier treatment groups,the D3 group’s whole fish crude protein content was significantly higher than the D2 group’s whole fish crude protein content(P<0.05).The results showed that both soybean oil or compound oil,fat source form,fatty acid composition and emulsifier treatment had no effect on the growth performance of tilapia.But blend oil or soybean oil with emulsifier are good for improving the nutritional value of tilapia.2.Serum biochemical indicators: There was no significant difference in T-CHO content between D1-D6 groups(P>0.05).And there were no significant difference between the groups of emulsifiers treatment(D1 and D2、D4 and D5)(P>0.05).The TG and LDL-C levels of serum in the groups fed with soybean oil powder(D2)and the blend oil groups(D4)were significantly lower than the groups fed with liquid soybean oil(D1)(P<0.05).The results show that fat powder and blend oil can reduce serum lipid levels,while emulsifier treatment has no effect on tilapia serum lipid levels.3.Serum and liver antioxidant enzyme activities: There were no significant difference in serum SOD and MDA of serum and liver levels in the fish fed D1-D6 groups.Between different fat source morphology treatment groups,the CAT activity of serum of emulsified blend oil powder group(D6)was significantly higher than the CAT activity of liquid blend oil groups(D5)(P< 0.05).The T-AOC of the liver in the soybean oil powder groups(D2)was significantly higher than the T-AOC of the liver in the liquid soybean oil group(D1)(P<0.05).Between different linoleic acid / linolenic acid ratio treatment groups,the serum and liver antioxidant indexes of tilapia in D1 and D4 groups were not significantly different(P > 0.05),but the liver CAT and SOD activities of fish in group D3 were significantly higher than those in group D6(P<0.05).Between the emulsifier treatment groups,the SOD of the soybean oil powder with emulsifier(D3)was significantly higher than the SOD of the group without emulsifier treatment(D2)(P<0.05).The results show that fat powder and emulsifier treatment could increase the antioxidant enzyme activity of tilapia.Soybean oil can increase tilapia liver antioxidant enzyme activity.4.Muscle texture and edible quality: There were no significant differences in springiness,chewiness,gumminess,resilience and cooking percentage among the D1-D6groups(P>0.05).Between different fat source morphology treatment groups,the hardness of the powder oil feed groups(D2 and D6)were higher than the corresponding liquid oil groups(D1 and D5).And the hardness of the D6 group was significantly higher than that of the D5group(P<0.05).The tenderness of soybean oil powder groups(D2)was significantly higher than the soybean oil group(D1)(P<0.05).Between different linoleic acid / linolenic acid ratio treatment groups,the tenderness of D4 group was significantly higher than that in D1group(P<0.05),and the p H of D6 group was significantly higher than that in D3 group.Between the emulsifier treatment groups,the water holding capacity of D3 group was significantly higher than that in D2 group.The p H of D5 group was significantly higher than that in D4 group.The results show that the fat powder,blend oil and emulsifier treatment can improve the muscle quality of tilapia.5.Fatty acid composition of muscle and liver: Between different fat source morphology treatment groups,the SFA of liver in the fat powder groups(D2 and D6)were significantly lower than the corresponding liquid oil groups(D1 and D5)(P<0.05).The n-3PUFA of liver in the D3 fed group was significantly higher than that in the D1 group(P<0.05).Between different linoleic acid / linolenic acid ratio treatment groups,the contents of liver SFA and MUFA in the blend oil groups were significantly higher than the soybean oil groups(P<0.05).The n-6 PUFA in muscle and liver of fish in the soybean oil groups were significantly higher than that in the blend oil groups(P<0.05).Between the emulsifier treatment groups,the SFA and n-3 PUFA content in liver of D5 group was significantly higher than that of D4 group(P<0.05).The SFA content in muscle of fish in group D5 was also significantly higher than that in group D4.The results show that the fat powder is beneficial to reduce the liver SFA content of tilapia and increase the n-3 PUFA content of tilapia liver.The blend oil can increase the content of SFA and MUFA in tilapia muscle.And emulsifier treatment can increase the n-3 HUFA and SFA content of tilapia.6.Liver lipid metabolism-related gene expression levels: Between different fat source morphology treatment groups,the fatp 5 and acox 1 expression of liver in the fat powder feed groups(D2 and D6)were significantly up-regulated compared to the liquid oil groups(D1and D5)(P<0.05).Between different linoleic acid / linolenic acid ratio treatment groups,the expression of fabp 4 in D4 and D6 feed groups were significantly up-regulated compared with the D1 and D3 groups(P<0.05).The expression of elovl 5 in the blend oil groups were significantly increased(P<0.05),especially,the expression of elovl 5 in D4 feed groups were significantly higher than that in the D1 groups(P<0.05).Between the emulsifier treatment groups,the expression levels of lpl,acc β,and hsl in D5 group were significantly higher than those in D4 group(P<0.05).The results show that fat powder can increase fatty acid transport and metabolic gene expression in tilapia.The blend oil can promote tilapia fat transport and expression of genes related to synthesis.And the emulsifier treatment can increase the expression of genes related to fatty acid transport in tilapia.In summary,the results of this study show that tilapia cultured on fat powder feeds show improved growth,health and muscle quality compared to liquid oil feeds.It means that fat powder can be used as a fat source for tilapia compound feed.The blend oil feed with a balanced fatty acid composition(linoleic acid to linolenic acid ratio)can improve the growth performance and health of tilapia.In this study,the ratio of linoleic acid to linolenic acid was preferably in 5:1,which could provide a more balanced fatty acid composition for tilapia feed.This study is the first use of fat powder in aquatic animal feed.From the advantages of fat powder and its extensive application in livestock and poultry feeds and the results of this study.It is worth carrying out breeding experiments and popularization in other aquatic animals.