The influence of feeding lactic acid bacteria LAB4012 strain on the growth and non-specific immunity of cobia
Date Issued
2014
Date
2014
Author(s)
Wang, Yow-Min
Abstract
Cobia (Rachycentron canadum) is an important fish species of cage-aquaculture industry, and has brought high economic interest in Taiwan. Cobias have been infected by many pathogens, such as vibrio and photobacteria. Antibiotics and vaccine are widely used for antagonizing bacteria pathogens, but the use of antibiotics made some drug-resistant strains of pathogens have been identified in the past few years, and the protection efficacies of vaccine were still unstable in field trials. Xing et al. (2013) demonstrated that lactic acid bacteria (LAB), Pediococcus pentosaceus LAB4012, which was derived from cobia’s intestine, could help cobia to antagonize photobacteria infection, but did not increase antibody titer of the Pdp-immunized cobia. Therefore, it is suggested that the LAB4012-induced protection against Pdp mainly rely on innate immunity. For understanding the tips of LAB4012 help cobia against Pdp, in this study, the influence of LAB4012-feeding in cobia was further examined, including the growth rate, density of intestine goblet cells, peripheral leukocytes and erythrocytes, and the expression level of inflammatory cytokines after Pdp challenge. Our results indicated that 2-week-LAB4012-feeding can significantly enhance the growth rate of smaller cobia with original body length of 12 cm, and the cumulated mortality of the fed cobia post Pdp challenge was 20% lower than that of the control group. After 4-week feeding with LAB4012, the density of goblet cells in cobia intestine villi was higher than that of control group, and the leukocyte density of the LAB-fed cobia was also higher than that of the control group. After Pdp immersion challenge, the density of the peripheral red blood cells (RBCs) in the LAB4012-fed cobia was stable. On the contrary, the RBCs level decreased in the control group at 1 day post infection (dpi) and restored at 3 dpi. Both LAB4012-fed cobia and control cobia, the leukocyte density increased after Pdp challenge, but their levels in LAB4012-fed group at 1 and 3 dpi were higher than that in the control group. The expression levels of IL-1β and TNF-α in liver and head kidney showed no difference between the LAB4012-fed group and the control group. After Pdp challenging, TNF-α expression level in the liver and both genes in head kidney were significantly up-regulated in LAB-feeding group. Therefore, we reconfirmed LAB4012 to be a probiotic for cobia due to speeding up the maturity of immune system through elevating the growth rate of smaller cobia, strengthen the intestinal mucus barrier through increasing the goblet cell density, and enhancing the expression of inflammation cytokines at the early stage of infection. In summary, LAB4012 can speed up the growth of smaller cobia and result in as a probiotic can improve non-specific immune system of cobias with increasing growth rate, inducing gut immunity, strengthening and regulating inflammation to against Pdp.
Subjects
Cobia
photobacteria
probiotics
growth rate
non-specific immune system
SDGs
Type
thesis
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