Effects Of Citric Acid And Microecologics On Growth Performance, Digestive Enzyme Activity And Immunity Of White Shrimp, Litopenaeus Vannamei

Exp.1Effects of citric acid on growth performance, digestive enzymeactivity and immunity of white shrimp, Litopenaeus vannameiThe present study was conducted to evaluate the effects of dietary citric acid on growthperformance, degestive enzyme and immunity of L.vannamei. Shrimps with initial bodyweight of5.57±0.21g were fed with basal diet supplemented with0%(control diet),0.1%,0.2%,0.3%,0.4%,0.5%citric acid for45days. Results showed that weight gain (WG) wasincreased by15.73%, feed conversion ratio (FCR) decreased by0.17and protein efficiencyratio (PER) increased by13.72%by the addition of0.2%citic acid in diet compared withcontrol group (P<0.05). The activities of hepatopancreas protease in0.2%,0.3%citric acidgroups tended to be higher (P>0.05), and activity of intestine protease in0.2%citric acidgroup was significantly higher (P<0.05) than those of control group. No significantdifference was found in intestine amylase activity among treatments (P>0.05). The activitiesof phenoloxidase (PO) in0.1%,0.2%,0.3%citric acid group, superoxide dismutase (SOD) in0.2%,0.3%,0.4%,0.5%citric acid group, lysozyme (LSZ) in0.2%,0.3%citric acid groupswere all significantly higher than those of control group (P<0.05). Accumulative mortalitiesof control group,0.1%,0.2%,0.3%citric acid group were80.0%,73.3%,60.0%,56.7%,respectively on the4th day after injection of Vibrio alginolyticus in the body of shrimp.0.2%and0.3%citric acid groups had significantly lower acumulative mortalities than controlgroup (P<0.05). Relative Percent Survival of the two groups reached25.0%,29.2%. Resultsabove showed that dietary citric acid could improve growth performance, digestive function,immunity function and resistence of L.vannamei to Vibrio alginolyticus. Thesupplementation level of citric acid in diet was sugested to be0.2%～0.3%for L.vannamei. Exp.2Effects of yeast culture and Bacillus on growth performance,protease activity and immunity of white shrimp, Litopenaeus vannameiA feeding experiment was conducted to investigate the effects of yeast culture and Bacilluson growth performance, protease activity and immunity of Litopenaeus vannamei. Fourexperimental diets were formulated by adding yeast culture (Yikang XP) and Bacillus inbasal diet (control diet):0.075%Yikang XP,0.100%Yikang XP,0.200%Bacillus. Shrimpswith initial body weight of5.57±0.21g were fed for45days.Results showed that weightgains (WG) were increased by17.24%,12.29%,20.18%, feed conversion ratio (FCR)decreased by14.28%,9.77%,12.03%and protein efficiency ratio (PER) increased by16.49%,10.05%,12.98%respectively by the addition of0.075%Yikang XP,0.100%YikangXP,0.200%Bacillus in diet compared with control group (P <0.05); No differences wereobserved in muscle composition among treatments (P>0.05); Hepatopancreas proteaseactivities in0.075%Yikang XP,0.100%Yikang XP,0.200%Bacillus group was25.24%,15.22%,54.92%higher than those of control group respectively (P <0.05), while intestinalprotease activities presented weak increasement (P>0.05); The activities of serumphenoloxidase (PO), lysozyme (LZM) and superoxide dismutase (SOD) in0.100%YikangXP and0.200%Bacillus group, were all significantly higher than those of control group (P <0.05); In the challenge trial, no significant defference was found in accumulative mortalitiesbetween control group and Yikang XP groups (P>0.05), while accumulative mortality inBacillus group was significantly lower than control group on1st,3rd,4th day after injectionwith Vibrio alginolyticus (P <0.05). Relative percent survival of0.200%Bacillus groupreached27.1%on the4th day after injection of V. alginolyticus. Results above showed thatdietary yeast culture and Bacillus could improve growth performance and digestive functionof L.vannamei, and Bacillus have obvious benificial effect on immunity function andresistence of L.vannamei to V. alginolyticus.Exp.3Effect of compounds formed from citric acid, Ballucis, Yikang XP,Azomite on growth performance, protease activity and immunity of whiteshrimp, Litopenaeus vannameiA feeding experiment was conducted to investigate the effects of compoundsformed from citric acid, yeast culture (Yikang XP), Bacillus, Azomite on growthperformance, protease activity and immunity of Litopenaeus vannamei. Four experimental diets were formulated by adding compounds to basal diet:0.3%citric acid+0.2%Bacillus,0.3%citric acid+0.1%Yikang XP,0.3%citric acid+0.4%Azomite,0.1%Yikang XP+0.4%Azomite. Shrimps with initial body weight of5.57±0.21g were fed for45days.Resultsshowed that weight gain (WG) increased by12.48%、16.55%（P<0.05）, feed conversionratio (FCR) decreased by11.03%、11.76%（P<0.05） and protein efficiency ratio (PER)increased by7.52%、12.00%（P<0.05） in0.3%citric acid+0.4%Azomite,0.1%Yikang XP+0.4%Azomite group respectively (P<0.05); The activities of protease in hepatopancreas inall of the compounds groups were significantly increased compared with control group(P<0.05), activities of SOD, LZM in experimental were significant higher than that of cantrolgroup (P>0.05); The Relative Percent Survival of0.3%citric acid+0.2%Bacillus,0.3%citricacid+0.1%Yikang XP,0.3%citric acid+0.4%Azomite,0.1%Yikang XP+0.4%Azomitegroup reached31.3%、37.5%、41.7%、18.8%respectively on the4th day after injection ofVibrio alginolyticus. Results above showed that compounds had little antagonism orsynergism on growth, but could evidently enhanced resistence of L.vannamei to Vibrioalginolyticus.