| In the present study,the theory basis is protein-spring of carbohydrate and lipid.Fish meal was replaced respectively by corn starch and soybean oil.Combined with methods of traditional nutrition and molecular biology,the purpose of this study was to evaluate the ability of common carp to utilize corn starch and soybean oil to replace protein by determining the effects of different levels of carbohydrate and lipid on growth performance,body composition,immunity,biochemical indices in serum,digestive enzymes activities,glucose and lipid metabolism enzyme activities and gene expression.What's more,it could also provide useful references for producing the low-nitrogen and high-efficiency feed of carp.1 Effect of different dietary protein and corn starch levels on the growth performance and gene expression of related metabolize enzyme in carp.A 63 days feeding trial was conducted to study the effects of dietary fish meal replaced by corn starch on the growth performance and related metabolism in carp(average initial body weight,36.12±1.18 g),aiming to ascertain the protein sparing effect of carbohydrate in diets of carp.900 fish were randomly distributed into 5 groups at a density of 60 fish per freshwater cages(1.0 × 1.0 × 2.0 m).Five kinds of diets were prepared with corn starch as the carbohydrate source to obtain corn starch levels of 0%,6.5%,13%,19.5%,or 26% and protein levels of 32%,30%,28.1%,26.2%,24.2%.Experimental diets were recorded as diet 1,diet 2,diet 3,diet 4,and diet 5.The results showed that the maximum growth was obtained in fish fed diet 1(32% crude protein,0% starch),and it was significantly higher than others(P<0.05).Hepatosomatie index(HSI)and concentration of liver glycogen increased with increasing dietary corn starch levels,and they were significantly higher in fish feed Diet 1than that of Diet 5(P<0.05).There were no significant differences in condition factor(CF)and whole body crude protein(P>0.05).Higher whole body crude lipid was observed in fish feed diet 4 and diet 5.Crude lipid in muscle was enhanced with increasing level of dietary carbohydrate,and peaked in fish fed the diet 4(P<0.05).Glucose concentration in plasma,triglyceride and cholesterol concentration increased with increasing dietary carbohydrate content.The immune function was enhanced when corn starch was included in diets appropriately.Higher activities of superoxide dismutase(SOD)and catalase(CAT),and lower activities of glutamic oxaolacetic transaminase(GOT)and glutamic propylic transaminase(GPT)were found in fish fed Diet 2 and Diet 3.There were no significant differences in lysozyme(LZM)and alkaline phosphatase(AKP)(P>0.05).Protease activity decreased with increasing dietary corn starch levels,but no significant differences were observed in treatment groups(P>0.05).Amylase and lipase activities reduced with increasing carbohydrate levels.Glucokinase(GK),hexokinase(HK)and pyruvate kinase(PK)activity significantly increased with increasing carbohydrate levels,while the glucose-6-phosphate(G6Pase)activity decreased with increasing carbohydrate levels(P<0.05).Three fish,which were fed commercial diet with 32% protein,were collected to determine the gene expression of GK and G6 Pase.108 fish were divided into two groups,which were low-carbohydrate group(including crude protein 30%,corn starch 6.5%)and high-carbohydrate group(including crude protein 24.2%,corn starch 26%)and each group had three replicates.Fish were fasted for 48 h.Then three fish per cage were collected at 0 h,3 h,6 h,12 h,24 h and 48 h after refeeding,and the hepatopancreas and intestine were removed.The results showed that GK gene expression was significantly higher in fish fed high-carbohydrate diet than that of low-carbohydrate group(P<0.05).GK gene expression increased first and then decreased in hepatopancreas and intestinal It reached a peak at 12 h after refeeding for every group.The G6 Pase gene expression of low carbohydrate group is higher than that in high carbohydrate group after refeeding.It peaked respectively at 3 h and 6h in hepatopancreas and intestine.Results suggested that the maximum growth was obtained in fish fed diet 1(32% crude protein,0% starch).The protein-sparing of corn starch in diets of carp was not available in this experiment.Immune function,digestive enzyme activity and metabolism enzyme activity were enhanced with incorporating corn starch properly,but the higher carbohydrate could increase the burden of metabolism and have bad influence on fish.2 Effect of different dietary protein and lipid levels on the growth performance and gene expression of related metabolize enzyme in carp.A 63 days feeding trial was conducted to study the effects of dietary fish meal replaced by soybean oil on the growth performance and related metabolism in carp(average initial body weight,36.12±1.18 g),aiming to ascertain the protein-sparing effect of lipid in diets of carp.900 fish were randomly distributed into 5 groups at a density of 60 fish per freshwater cages(1.0 × 1.0 × 2.0 m).Five kinds of diets were prepared with soybean oil as the lipidsource to obtain lipid levels of 2.1%,4%,5.8%,7.6%,or 9.4% and protein levels of 32%,31.1%,30.2%,29.2%,or 28.3%.Experimental diets were recorded as diet 1,diet 2,diet 3,diet 4,and diet 5.The results showed that the maximum growth was obtained in fish fed diet4(29.2% crude protein,7.6% crude lipid).Hepatopancreas index(HSI)and concentration of liver glycogen increased with dietary soybean oil levels increasing,and they were significantly higher in Diet 5 group than that in Diet 1 group(P<0.05).There were no significant differences on condition factor(CF)(P>0.05).Blood sugar,,triglyceride,cholesterol and low density lipoprotein level improved with dietary soybean oil content increasing.The high density lipoprotein level rised in the first stage,and then decreased.which in Diet 3 reached highest.The immune function was enhanced with increasing soybean oil levels.There were higher activities of superoxide dismutase(SOD)and catalase(CAT),but lower malondialdehyde(MDA)when soybean oil was included the diet appropriately.The tread of glutamic oxaolacetic transaminase(GOT)and glutamic propylic transaminase(GPT)activities decreased and then increased,and it reached a minimum in Diet 2.There were no significant differences in alkaline phosphatase(AKP)and lysozyme(LZM)(P>0.05).Lipase activity was significantly affected by dietary soybean oil levels in hepatopancreas and intestinal(P<0.05).Lipase activity in fish fed Diet 3 was significantly higher than others in hepatopancreas(P<0.05).There were no significant differences in amylase and protease activities(P>0.05).Hepatic lipase(HL)and lipoprotein lipase(LPL)activity significantly increased with increasing lipid levels,while the fatty acid synthase(FAS)activity decreased with increasing lipid levels(P<0.05).Three fish,which were fed commercial diet with 32% protein,were collected to determine the gene expression of FAS and LPL.108 fish were divided into low-lipid group(including crude protein 31.1%,soybean oil 2.0%)and high-carbohydrate group(including crude protein 29.2%,soybean oil 6.0%).Each group had three replicates and fsated 48 h.Hepatopancreas and kidney from three fish per cage were collected at 0 h,3 h,6 h,12 h,24 h and 48 h after refeeding.The results showed that FAS gene expression was siginificantly higher in low-lipid group than that in high-lipid group.The FAS gene expression decreased and then increased,and reaching a peak at 6 h in hepatopancreas.The LPL gene expression of low lipid group was higher than that in high lipid group after refeeding.LPL gene expression increased from refeeding o h to 6 h and then decreased in hepatopancreas,and increased from0 h to 24 h and then decreased in kidney.Both of them decreased to the level of fasting.The results suggested that the maximum growth was obtained in diet 4 group(29.2%crude protein,7.6% lipid).Immune function,digestive enzyme activity and metabolic enzyme activity were enhanced by proper soybean oil level,but the too high lipid level could increase the burden of metabolism and have bad influence on health of fish. |
PDF Full Text Request