en aquaculture aquaculture پژوهشي Orginal research papers <span style="font-size:12.0pt"><span new="" roman="" style="font-family:" times="">The effect of different concentrations of <i>Ocimum basilicum</i> extract supplement on growth and survival of Western white leg shrimp (<i>Litopenaeus vannamei</i>), juveniles was investigated. Shrimps were separated into four experimental groups of <span style="color:#0070c0">0 (</span>Controls), 60, 120 and 240 ppm extracts of <i>O. basilicum</i>. <span style="color:red">The photoperiod was regulated to a 12:12 dark/light cycle and molts, feces and dead shrimps were daily removed and 30% of water in each tank was exchanged by new sea water. Biometry was done once a week</span>. Extract supplemented diet did not have any significant effect on weight gain (%), final weight (g), growth performance, feed utilization and body composition of <i>L. vannamei</i> when compared to shrimp in the control diet. It was also observed that the shrimp fed the diet containing 120 ppm <i>O. basilicum</i> extract obtained the highest weight gain (%) 6.23 &plusmn; 0.12% and the lowest rate (5.7 &plusmn; 0.1%) was for 240 ppm extract. In conclusion, dietary <i>O. basilicum</i> extract supplementation had no significant effects on the growth performance, survival rate, feed utilization and carcass composition of Western white leg shrimp juveniles.</span></span> <span style="font-size:12.0pt"><span new="" roman="" style="font-family:" times=""><span style="color:red">The positive results obtained encourage conducting further research on the administration of <i>O. basilicum</i> extract on Western white leg shrimp or other economically important species but with longer duration of culture period.</span></span></span> Litopenaeus vannamei, Basil extract, Growth, Survival rate, Body composition 487 492 http://jifro.ir/browse.php?a_code=A-10-132-2&slc_lang=en&sid=1 L. Mosavi dehmordi lalehmosavi84@yahoo.com 100319475328460047799 100319475328460047799 Yes Department of Fisheries, Faculty of Natural Resources, Behbahan Khatam Alanbia University of Technology,Behbahan,Iran R. Gholipour rezigholiupour@gmail.com 100319475328460047800 100319475328460047800 No Department of Fisheries, Faculty of Natural Resources, Behbahan Khatam Alanbia University of Technology,Behbahan,Iran S. Ziaeinejad zbsaeed@yahoo.com 100319475328460047801 100319475328460047801 No Department of Fisheries, Faculty of Natural Resources, Behbahan Khatam Alanbia University of Technology,Behbahan,Iran M. Sori Msouri2008@yahoo.com 100319475328460047802 100319475328460047802 No Khuzestan fisheries administration,Abadan,Iran