Effect Of Carbohydrate Source,Carbohydrate/Protein Ratio And Feeding Frequency On Growth Performance And Carbohydrate Metabolism Of Common Carp(Cyprinus Carpio)

Feeding trials were carried out to investigate the effects of nutritional physiology of different carbohydrate type,carbohydrate to protein ratio,different feeding frequencies on growth performance,feed utilization,digestive enzyme activities of intestine and hepatic carbohydrate metabolic enzyme activities,regulatory factor contents related to glycometabolism,the IR,GLUT2 and HK m RNA expression levels in hepatopancreas,and the GLUT2 and SGLT1 m RNA expression levels in intestine.Outcomings of this study are presented as listed below:1.Effect of dietary carbohydrate source and carbohydrate/protein ratios on growth and carbohydrate metabolism of common carpAn 8-week feeding experiment was designed to value the effect of dietary carbohydrate/protein ratio on growth performance,feed utilization,digestive enzyme activities of intestine and hepatic carbohydrate metabolic enzyme activities,regulatory factor contents related to glycometabolism,the IR,GLUT2 and HK m RNA expression levels in hepatopancreas,and the GLUT2 and SGLT1 m RNA expression levels in intestine of common carp with the initial body weight of(55.73±3.55)g.Isolipidic,isoenergetic diets with C5%/P32%,C10%/P30%,C20%/P28% carbohydrate/protein ratio were assessed.The carbohydrate source was cassava starch(CS)and wheat starch(WS),respectively.The results were presented as follow:(1)In the condition of C5% /P32% and C10% /P30% fish fed the WS diet had significantly higher weight gain rate(WGR)and specific growth rate(SGR),significantly lower feed conversion ratio(FCR)and hepatosmatic index(HSI)compared to those fed the CS diet(P<0.05).However,in the condition of C20% /P28%,better WGR,SGR,protein efficient ratio(PER)and condition factor(CF),lower FCR and HSI were observed in CS group,but there were no significant differences of these parameters among fish fed with two carbohydrate source group(P>0.05).(2)In the condition of the low or high C/P,the significantly higher protease activities of foregut and midgut,amylase activities of foregut,midgut and hindgut were observed in the CS group(P<0.05),while the significantly higher lipase activities of midgut were found in the WS group(P<0.05).(3)In the condition of C20%/P28% fish fed the CS diet had significantly higher phosphofructokinase(PFK)and pyruvate kinase(PK)compared to those fed the WS diet(P<0.05).And in the condition of C20%/P28%,the significantly higher insulin content in serum appeared in the CS group(P<0.05).(4)In the condition of the low or high C/P,the GLUT2 m RNA expression level of hepatopancreas and SGLT1 m RNA expression level of intestine in the CS group were significantly higher than those of WS group(P<0.05).According to the above observations,under the circumstance of the appropriate dietary carbohydrate to protein ratio,cassava starch and wheat starch have superior protein-sparing effect.2.Effect of dietary carbohydrate/protein ratios and feeding frequency on growth and carbohydrate metabolism of common carpA 8-week 3×2 two-factorial experiment was conducted to investigate effects of dietary carbohydrate to protein ratio(C5%/P32%,C10%/P30%,C20%/P28%)and feeding frequencies(fourth daily and twice daily)on the growth performance,feed utilization,digestive enzyme activities of intestine,hepatic carbohydrate metabolic enzyme activities,regulatory factor contents related to glycometabolism,the IR,GLUT2 and HK m RNA expression levels in hepatopancreas,and the GLUT2 and SGLT1 m RNA expression levels in intestine of common carp [initial average weight of(55.37±3.55)g] cultured in floating net cages.Three replicates with 150 common carp were randomly allotted to one treatment with combination of dietary carbohydrate level and feeding frequency in a complete randomized design.The outcomings indicated that:(1)The growth performance and feed utilization of the fish was significantly affected only by feeding frequency(P<0.05).As feeding frequency increasing,WGR,SGR,PER,and CF significantly rose(P<0.05).However,HSI was significantly affected by dietary C/P ratio,feeding frequency and the interaction of both.HSI declined significantly with the increasing feeding frequency(P<0.05),while HSI rose significantly with the increasing C/P ratio,and there were significant difference between the fish fed with the C5%/P32% and C20%/P28% diets(P<0.05).(2)Feeding frequency had significant effect on protease activities of foregut,amylase and lipase activities of midgut.Protease activities of foregut of fish fed fourth daily were significantly higher but amylase and lipase activities of midgut of fish fourth daily were significantly lower than those fed twice daily(P<0.05).In addition,dietary C/P ratio had significant effect on the protease and amylase activities of midgut.Significant effect on protease activities of midgut of fish fed with C10%/P30% diet was found,compared to the other groups(P<0.05).(3)The PFK and G6 PD activities were significantly affected only by dietary C/P ratio,and there was a significant negative correlation between those activities and dietary C/P ratio(P<0.05).In addtion,The PEPCK and GS activities were significantly affected by dietary C/P ratio and feeding frequency,and there was a significant positive correlation between those activities and dietary C/P ratio,and a significant negative correlation between them(P<0.05).(4)Dietary C/P ratio and feeding frequency had significant impact on the INS,GC,GH,GLU,IR,and IGF-1 contents(P<0.05).(5)The IR,GLUT2 and HK m RNA expression levels of hepatopancreas and GLUT2 and SGLT1 m RNA expression levels of intestine were significantly affected by dietary C/P ratio and feeding frequency(P<0.05).Those expression levels all presented the trend of significant increase with increasing feeding frequency(P<0.05).Furthermore,the highest values of those expression levels was observed in the C10%/P30% group and these were significantly higher than those in other groups(P<0.05).Combined the results of this study,under this study conditions,the C10%/P30% diet is suitable for common carp,and its feeding frequency is fourth daily.3.Effect of carbohydrate source and feeding frequency on growth and carbohydrate metabolism of common carpThe effects of cassava starch,modified starch and feeding frequency on the growth performance,feed utilization,digestive enzyme activities of intestine,hepatic carbohydrate metabolic enzyme activities,regulatory factor contents of glycometabolism,the IR,GLUT2 and HK m RNA expression levels in hepatopancreas,and the GLUT2 and SGLT1 m RNA expression levels in intestine was studied in common carp.Three isonitrogenous and isoenergetic diets were formulated with three starch sources(cassava starch,pregelatinized cassava starch and cassava acetate starch,i.e.CS,PCS,CAS)with 20%,and each diet was fed fourth daily and twice daily at the rate of 4% of the fish wet body weight.Three replicates with 150 common carp [initial average weight of(55.37±3.55)g] were randomly allotted to one treatment with combination of dietary carbohydrate level and feeding frequency in a complete randomized design.The result were presented as follow:(1)The growth performance and feed utilization of the fish was not affected by dietary starch source and feeding frequency(P>0.05).Fish fed with pregelatinized cassava starch showed the highest WGR,SGR,PER,HSI,CF,and the lowest FCR(P>0.05).In addition,WGR,SGR and PER of fish fed fourth daily were higher but FCR of fish fourth daily were lower than those fed twice daily(P>0.05).(2)Diets supplemented with pregelatinized cassava starch boosted amylase and lipase activities of intestine in comparison to those supplemented with cassava starch,and cassava acetate starch(P<0.05).Feeding frequency had significant impact on protease activities of foregut,amylase and lipase activities of intestine(P<0.05).(3)Activities of PFK and PK reached the highest in the pregelatinized cassava starch group(P<0.05).Activities of PEPCK and GS reached the lowest in the pregelatinized cassava starch group(P<0.05).Besides,the PFK,PK,PEPCK and GS activities were significantly affected by feeding frequency(P<0.05).(4)Compared other starch groups,the contents of GLU,INS,GC and IGF-1of serum in the pregelatinized cassava starch group were significantly increased(P<0.05),while the contents of GH in the pregelatinized cassava starch group were significantly decreased(P<0.05).Besides,the GLU,INS,IR and IGF-1 contents were significantly affected by feeding frequency(P<0.05).(5)Compared to the other strarch groups,the significant higher peaks of the IR,GLUT2 and HK m RNA expression levels of hepatopancreas and GLUT2 and SGLT1 m RNA expression levels of intestine were observed in the pregelatinized cassava starch group(P<0.05).Besides,as feeding frequency increasing,those expression levels rose significantly(P<0.05).The findings indicated that under the conditions in present experiment,pregelatinized cassava starch are better for the growth of common carp than cassava starch,and cassava acetate starch,thus pregelatinized cassava starch should be the optimal carbohydrate source,and appropriate increasing feeding frequency can enhance the ability to utilize cassava starch and modified starch for common carp.