Function Of Vitamin D3 In Growth And Resistance To Decapod Iridescent Virus 1(DIV1) In Litopenaeus Vannamei

Decapod iridescent virus 1（DIV1）has caused significant economic losses to the shrimp aquaculture industry.As a prohormone,vitamin D3（VD3）is metabolized to25-hydroxyvitamin D3 in the liver,and then to 1,25-dihydroxyvitamin D3（1,25（OH）₂D3）in the kidney,which binds to nuclear receptors（VDR）to perform related functions including promoting growth and enhancing the body’s immunity.However,there are currently few reports on the ability of VD3 in the growth and antiviral function of Litopenaeus vannamei.Based on this,this study takes L.vannamei as the research object to explore the effects of VD3 and its active form 1,25（OH）₂D3 on the growth and anti DIV1 ability of L.vannamei.Firstly,the effects of VD3 and 1,25（OH）₂D3 on growth performance and survival rate of L.vannamei were investigated in a 5-week feeding experiment.A total of 810shrimps（initial weight 0.68±0.10 g）were randomly divided into 9 groups with 3replicates per group and 30 shrimps per replicate.On the basis of commercial diet,different VD3 diets（0,0.10,0.30,0.40 and 0.80 mg/kg）and 1,25（OH）₂D3 diets（2.00,6.00,8.00 and 16.00μg/kg）were formulated for feeding.The results showed that feeding0.30 mg/kg VD3 and 8.00μg/kg 1,25（OH）₂D3 significantly improved the growth performance of L.vannamei（p<0.05）.The optimal demand for VD3 based on percentage gain（PWG）,specific growth rate（SGR）,and feed utilization rate（FE）is 0.37mg/kg,and the optimal demand for 1,25（OH）₂D3 is 10.39-10.42μg/kg.In addition,VD3（0.10,0.30,0.40 mg/kg）and 1,25（OH）₂D3（8.00μg/kg）significantly increased the survival rate of L.vannamei compared with the control group.Subsequently,it was verified that VD3 and 1,25（OH）₂D3 could enhance the ability of L.vannamei to resist DIV1.L.vannamei was treated with VD3（0.30 mg/kg and 0.80mg/kg）for 1d,5 d and 10 d,respectively,and L.vannamei was treated with1,25（OH）₂D3（2.00μg/kg,6.00μg/kg,8.00μg/kg and 16.00μg/kg）for 10 d,and then the DIV1 infection experiment was carried out.The results were counted every 3h to calculate the cumulative elimination rate of shrimp.The results showed that VD3（0.30mg/kg）could significantly improve the anti-DIV1 ability of L.vannamei（p<0.05）,and1,25（OH）₂D3（6.00μg/kg）could also significantly improve the survival rate of L.vannamei infected with DIV1（p<0.05）.