en fish disease fish disease پژوهشي Orginal research papers <span style="font-size:11pt"><span style="background:white"><span style="line-height:112%"><span style="tab-stops:45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt"><span style="font-family:Calibri,sans-serif"><i><span style="font-size:12.0pt"><span style="line-height:112%"><span new="" roman="" style="font-family:" times=""><span style="color:black">Lactobacillus brevis</span></span></span></span></i><span style="font-size:12.0pt"><span style="line-height:112%"><span new="" roman="" style="font-family:" times=""><span style="color:black"> was isolated from the intestinal tract of <i>Sander lucioperca</i> and its immunological parameters as well as intestinal morphology were studied. Thereafter, the fish were challenged with 4.5&times;10⁸ CFU/g<i> Aeromonas hydrophila</i>. The fish were monitored daily and the rate of survival was recorded over a period of 7 days post-challenge. The results showed that feeding with supplemented <i>L. brevis</i> (10⁸ to 10¹⁰ CFU/g) had significant effect (<i>p</i><0.05) on the survival rate. The serum lysozyme, alternative complement activity (ACH50) and IgM was significantly enhanced by dietary probiotics during the feeding period and post challenge compared to the control group. The serum IgM levels of dietary supplementation of <i>L. brevis</i> were significantly higher than that of the control after 8 weeks (<i>p</i><0.05). After 60 days total bacteria and probiotics in the intestinal tract in groups fed with doses of 10⁸ to 10¹⁰ CFU/g <i>L. brevis</i> had increased ratio in compare with control sampels. The survival rates after dietary administration of <i>probiotics</i> were significantly higher than that in control in post challenge. The probiotic (10¹⁰ CFU g^-1) can be used as an effective bio-control agent and as an immune stimulant in aquaculture.</span></span></span></span></span></span></span></span></span> Lactobacillus brevis, Sander lucioperca, Intestinal morphology, Immune parameters, Aeromonas hydrophila 387 402 http://jifro.ir/browse.php?a_code=A-10-1812-2&slc_lang=en&sid=1 M. Faeed m_faeed@yahoo.com 100319475328460045532 100319475328460045532 Yes Iranian Fisheries Sciences Research Education and Extension Organization(AREEO) R. Kasra Kermanshahi rkasra@yahoo.com 100319475328460045533 100319475328460045533 No microbiology M. PourKazemi mpourkazemi17@yahoo.com 100319475328460045534 100319475328460045534 No Iranian Fisheries Sciences Research Education and Extension Organization(AREEO) M. Ahmadnezhad m_ahmadnezhad@yahoo.com 100319475328460045535 100319475328460045535 No Iranian Fisheries Sciences Research Education and Extension Organization(AREEO)