Effects Of Poly-β-hydroxybutyrate On Few Important Traits And Gene Expression In The White Shrimps,Litopenaeus Vannamei

The Litopenaeus vannamei were selected from Yellow sea fisheries research institute Chinese academy of fishery science(Qingdao,Shandong).This study used the single factor concentration gradient method.The L.vannamei was fed with basal bait contained different concentrations of poly-β-hydroxybutyrate(PHB).This present study was aimed to investigate the influence of PHB on the growth performance,non-special immunity and the resistance to disease in Litopenaeus vannamei.1.Two hundred seventy shrimps were divided into six groups(in triplicate).The shrimps were fed with diet in different PHB concentrations(0.0%,0.5%,1.0%,2.5%,5.0%and 10.0%).After feeding PHB for 6 weeks,the survival rate,growth rate and the activity of non-special immunity enzyme were measured.The results showed that PHB had no effects on survival rate.But this indicated that the diet supplemented with 1%and 2.5%PHB induced a gain of the initial white shrimps weight with a factor 3.4 and 3.5 respectively,relative to a factor 3.2 in the no PHB feed group(P<0.05).The study also suggested that PHB could improve the ability of connatural immunity.It found that the activity of the total antioxidant capacity(T-AOC),superoxide dismutase(SOD),catalase(CAT),peroxidase(POD),lysozyme(LZM)and acid phosphatase(ACP)were increased in different degrees.From the result,the 1.0%-2.5%PHB was the best for the shrimps to improve the growth performance.2.The shrimps supplied with 0.0%and 2.5%PHB were selected to conduct the ammonia stress test.The shrimps were tested in the water with 15 mg/L concentration of ammonium nitrogen.After the stress test with NH4C1,the malonaldehyde(MDA)concentration was compared as well as the relative gene expression level presented in tissues by real-time PCR.After the ammonia stress test,it was found that the MDA concentration in shrimps fed with PHB was lower than that fed without PHB,especially difference was the significant in haemolymph(P<0.05).Furthermore,the gene expression level was higher in the experimental group than the blank group.The present study showed that PHB in feed had a certain protective effect.3.The experiment consisted of 6 tanks(in tuplicate,30 shrimps/share).All shrimps were fed at a daily ration of 5.0%BW on wet body weight per day in 4 weeks.After 4 weeks,the grown cultures of Vibrio anguillarum were washed in filtered and autoclavedPBS and injected into the shrimps at 108 CFU.3 shares of each treatment were used to calculate the morality rate,3 shares for sampling.After the challenge with V.campbellii,the group with the highest relative percent survival(RPS)and the control groups were selected to compare the gene expression in 48 h.The experimental results showed that the survival rate was up after a first rise and down.And the mean survival time and the gene relative expression level of the shrimps fed with PHB were higher than the shrimps without PHB.The data indicated that PHB could enhance the ability of shrimp resistance to V.campbellii infection.4.This research was conducted to test the effects of poly-β-hydroxybutyrate(PHB)on anti-WSSV and relative expression of non-special immune genes in Litopenaeus vannamei with WSSV infection.L.vannamei was supplied with 0.0%,0.5%,1.0%,2.5%,5.0%and 10.0%PHB in artificial compound feed at a daily ration of 5.0%BW in 20 days before WSSV infecction.After WSSV challenge,the survival rates,mean survival time,relative percent survival(RPS)and WSSV copies were compared.The gene relative expression level was analyzed by quantitative real-time reverse transcription PCR(QT-PCR).The results showed that there was no difference of survival rates among different treatments(P>0.05),nevertheless,the mean survival time of shrimps fed with PHB was higher than the control group.And the mean survival time of shrimps fed with 1.0%PHB was the highest;it was significant higher than the shrimps supplied with 0.0%PHB and 5.0%PHB in addition.The WSSV copies of experiments shows a rise after a first downward trend as the concentration of PHB increased at the prophase.It concluded that PHB could improve the immunity and the ability of anti-WSSV.