| The paper investigates the effect on the growth performance,antioxidant capacity,dry dew resistance and feeding behavior of P.clarkii by adding different doses of microbial-derived antioxidant to the pellet feed of P.clarkia.The appropriate amount of microbial source antioxidant added to feed in long-term breeding of P.clarkii and reasonable feeding time of microbial antioxidant diet were preliminarily obtained.This also provides a certain theoretical basis and practical reference for the use of microbial-derived antioxidant in the pellet feed of P.clarkii.1.Effect of different doses of microbial-derived antioxidant in feed on growth,antioxidant enzyme activity and anti-dry dew ability of P.clarkiiIn this study,two hundred and forty juveniles were cultured for 70 days by adding 0%,0.25%,0.5%,1%,and 1.5% dose of microbial-derived antioxidant(respectively labeled as A1-A5)to pellet feed.The metabolite of the microbial-derived antioxidant mainly includes VC、VE、SOD、glutathione and other antioxidant component.The results displayed that there was no significant difference in survival rate(SR),meat yield(MY)and hepatopancreas index(HSI)between the groups(P>0.05),and the weight gain rate(WGR)of A5 was significantly lower than that of other groups,and the shedding cycle was significantly longer than that of other groups(P<0.05).The antioxidant capacity of A4-A5 was higher than that of control group,in hepatopancreas,the T-SOD activity of A3-A5 group was significantly higher than A1 group,the MDA content of A4-A5 group was significantly lower than A1 group,and T-AOC and GSH-PX activity were significantly higher than A1 group(P<0.05);in serum,the T-AOC activity of A5 group was highest,the T-SOD and GSH-PX activity of A4-5 group were significantly higher than A1 group(P<0.05).After the 70 d breeding experiment,fifteen shrimps were selected from each experimental group for dry dew stress experiment at(21.3±0.7)℃ and relative humidity(39.25±0.89)%,and the survival rate of A4-A5 group was the highest after 24 h of dry dew.In hepatopancreas,the MDA content of A4-A5 group was significantly lower than that of A1 group,the lactic acid(LD)content and lactate dehydrogenase(LDH)activity of A2-A5 group were significantly lower than those of A1 group,and the activity of succinate dehydrogenase(SDH)was higher than A1 group(P<0.05);in muscle,LD content and LDH activity were significantly lower in A2-A5 group than in A1 group and SDH activity was significantly higher than in the A1 group(P<0.05).These results indicate that long-term supplement of microbial antioxidant can affect the growth of P.clarkii.The weight gain rate、antioxidant and dry dew resistance were considered,and the suitable amount of microbial source antioxidant in pellet feed was 1%.2.Effect of different feeding time of microbial antioxidant feed on growth,antioxidant capacity and dry dew resistance of P.clarkiiOn the basis of the above experimental results,the appropriate feeding time of the feed supplemented with microbial antioxidant was further explored.The experiment designed a control group(0% microbial-derived antioxidant)and an antioxidant group(1.5% microbial-derived antioxidant)with one hundred and fifty shrimps per experimental group,with three replicates.Eighteen shrimp were randomly selected from each group and the growth data were counted after 7,14,21 and 28 days feeding,and eighteen shrimp were selected in each feeding time for dry dew stress experiment.The results showed that there was no significant difference in SGR,HIS between the two groups after 7d,14 d and 21 d feeding(P>0.05),and the WGR and SGR of the antioxidant group were lower than the control group after 28 days feeding(P<0.05).There was no difference in the four antioxidant enzymes between the two groups hepatopancreas and serum after 7 and 14 days feeding(P>0.05).The T-SOD,GSH-PX and T-AOC activity of antioxidant group hepatopancreas was higher than control group(P<0.05)and the GSH-PX and T-AOC activity of antioxidant group serum was significantly higher than control group when feed for 21 days(P<0.05).There was no difference in the survival rate and body metabolic enzyme after the same dry dew time between two groups after 7 and 14 days feeding(P>0.05),and the survival rate of the antioxidant group after dry dew was significantly higher than that of the control group after 21 days feeding.After 21 days feeding,it was found that the LD content and LDH activity of body in antioxidant group were lower than control group(P<0.05).In summary,feeding P.clarkia with 1.5% microbial source antioxidant had a negative impact on the growth of shrimp after 28 days feeding,and the antioxidant enzyme activity and anti-dry dew ability of shrimp were significantly improved after feed for 21 days.3.The effect of microbial-derived antioxidant added to feed on the feeding behavior of P.clarkiiIn the study,we explored the possible reason for the effect of long-term feeding with higher dose of microbial antioxidant on the growth of P.clarkii by analyzing the feeding behavior on two kinds of diet.In the experiment,the feeding behavior of P.clarkia under the condition of satiety and starvation were observed,the two feeds were the control group(0% microbial source antioxidant)and the antioxidant group(1.5% microbial source antioxidant).The results showed that under the condition of not starvation,the feeding time and food-seeking time of the antioxidant group were significantly longer than those of the control group(P<0.05),and the dietary willingness of antioxidant group was significantly weaker than that of control group(P<0.05),and feeding intake of antioxidant group was lower than control group(P<0.05)after the shooting experiment.In the case of hunger,there was no significant difference in feeding time,food-seeking time and feeding intention between the two groups(P>0.05),and feeding intake of antioxidant group was still lower than control group(P<0.05).These results indicated that the palatability of the diet supplemented with antioxidant was worse than that of the control diet,which may be the main reason affecting the growth of P.clarkii after long-term feeding. |
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