Effects Of Three Different Temperatures On Lipid Requirement And Metabolism Of GIFT,Oreochromis Niloticus

1.The Genetically Improved Farmed Tilapia(GIFT,Oreochromis niloticus)strain is one of the most successfully farmed tilapia in China for its strong adaptability,rapid growth,high fecundity and broad diet.Our objective was to determine the optimal dietary lipid requirement of advanced juvenile GIFT rearing in 34 ℃ water temperature.In this experiment,360 fish with average initial body weight of(50.88±1.57)g were randomly divided into 6 groups with 3 replicates of 20 fish in each replicate.Each group was fed a diet containing either actual lipid level 0.22%(control group),2.83%,4.98%,7.45%,9.22% and 12.47%,respectively.Fish were fed three times daily(8:30,12:30 and 16:30)to apparent satiation for 56 days.At the end of feeding trial,growth performance,body composition,serum biochemical indexes and lipid metabolism enzyme activities were measured.The results showed as follows: with the increase of lipid levels,weight gain rate(WGR),and protein efficiency rate of GIFT were increased at first and then decreased.Broken-line regression analysis showed the best lipid level which could acquire the best WGR was 4.92%,and dietary lipid level for the lowest feed conversion ratio(FCR)was 5.46%.Increasing dietary lipid levels contributed to increased whole body lipid levels.Serum total cholesterol and triglyceride levels were the lowest in the group fed 4.98% lipid,broken-line regression analyses showed the optimum lipid requirements for minimum TG levels was 5.48%.Meanwhile,high density lipoprotein cholesterol content increased as the level of lipid increased.When the lipid level was between 4.98%-7.45%,the GIFT had the lowest content of low density lipoprotein cholesterol.Lipoprotein lipase(LPL),and hepatic lipase(HL)activities tended to first increase and then decrease as the level of dietary lipid increased,when liver lipase increased as the level of lipid increased.Our comprehensive analysis of growth performance,serum biochemical indexes and lipid metabolism enzyme activities suggests that the optimal level of dietary lipid for advanced juvenile GIFT between 4.92% and 5.46%.2.Our objective was to determine the optimal dietary lipid requirement of advanced juvenile GIFT rearing in 22 ℃ water temperature.In this experiment,360 fish with average initial body weight of(50.70±1.30)g were randomly divided into 6 groups with 3 replicates of 20 fish in each replicate.Each group was fed a diet containing either actual lipid level was 0.22%(control group),2.83%,4.98%,7.45%,9.22% and 12.47%,respectively,for 56 days.Fish were fed three times daily(8:30,12:30 and 16:30)at 22℃ water temperature to apparent satiation for 56 days.At the end of feeding trial,growth performance,body composition and serum biochemical indexes were measured.The results showed as follows: with the increase of lipid levels,weight gain rate(WGR),and protein efficiency rate of GIFT were increased at first and then decreased.Broken-line regression analysis showed the best lipid level which could acquire the best WGR was 6.98%,dietary lipid level for the lowest feed conversion ratio(FCR)was 7.48% and dietary lipid level for the highest protein efficiency rate(PER)was 7.48%.Increasing dietary lipid levels contributed to increased whole body lipid levels,when dietary lipid level reached 7.45%,the crude lipid of muscle was significantly higher than that of the control group.Serum total cholesterol and triglyceride levels were decreased at first and then increased.Meanwhile,high density lipoprotein cholesterol content increased then decreased as the level of lipid increased,the GIFT had lower content of low density lipoprotein cholesterol than the control group.Our comprehensive analysis of growth performance and serum biochemical indexes in muscle and liver suggests that the optimal level of dietary lipid for advanced juvenile GIFT between 6.98% and 7.48%.3、540 fish with average initial body weight of(50.90±1.60)g were selected and randomly divided into nine groups.The lipid levels were fed at three temperature levels(22°C,28°C,34°C)and were 2.83%,7.45% and 12.47% of diets were used to study the effects of temperature and lipid levels on the growth and related gene expression of tilapia.The main results were as follows: Water temperature and feed lipid levels significantly affected the growth rate,feed efficiency,and protein efficiency of tilapia.There was no significant difference in weight gain rate and specific growth rate between the 2.83% and 12.47% groups,but it was significantly lower than that of the 7.45% group.The feed coefficient of the 7.45% group was significantly higher than that of the other two groups,and the protein efficiency showed the opposite trend,2.83% and 12.47.The % group was significantly lower than the 7.45% group.From the temperature point of view,the weight gain rate and specific growth rate of the 22°C and 28°C groups were significantly lower than those of the 34°C group.However,the protein efficiency of the 28°C group was significantly higher than that of the other two groups,and the feed coefficient showed the opposite trend.The results showed that there was no significant interaction between temperature and lipid levels in the feed on the growth performance of tilapia.Water temperature and feed lipid significantly affected the m RNA expression levels of lpl and igf-I genes in tilapia.The expression level of lpl m RNA was significantly higher at 28°C and 12.47% lipid than that of other groups.The igf-I m RNA expression level was significantly higher at 34°C and 12.47% lipid than that of the other groups.According to the results of the study on the growth and titer of liver-related genes in tilapia,the water temperature and feed lipid content significantly affected the growth of tilapia and the m RNA expression of hepatic igf-I and lpl genes in the liver,affecting the lipid metabolism of the fish.When breeding,care should be taken to raise the water temperature and the amount of lipid added to avoid excessive deposition of lipid and cause adverse effects on fish.