Abstract
This work aimed to investigate the role of some immunostimulants and probiotics in improving the response of overwintered tilapia to Aeromonas hydrophila vaccine. In this study, 15000 Nile tilapia fry (Orechromis niloticus) were collected and divided into five groups. Group 1 was the control, groups 2 to 5 were fed diet supplemented with garlic, Echinacea, Organic GreenTM and Vet-YeastTM respectively for 5 months. Vaccination with A. hydrophila bacteria was done by the end of the feeding experiment. The antibody titer of the vaccinated overwintered tilapia of all groups showed no significant changes during the same sampling time. A significant high value in the antibody titer was recognized in vaccinated overwintered tilapia at the end of 6th-8th week post-vaccination (PV) in the control group and between the 4th – 8th week PV in the immunostimulant supplemented groups (Groups 2-3), and between the 2nd – 10th week PV in probiotic supplemented groups (Groups 4 and 5). The challenge infection of the vaccinated tilapia showed the highest mortality in Group 1 while the lowest mortality was seen in Group 5. However, maximum protection after challenge was seen at 6th week PV in other treated groups. The immunostimulants and probiotics under test proved efficient in improving the immune response to vaccination which will improve the resistance of tilapia fry against infection during the winter. The overall results are promising to implement overwintering fry culture program to economically maximize and efficiently use the available aquaculture facilities throughout the year. Key words: Tilapia, overwintering, immunostimulants, probiotics, vaccines, pathogens.
Highlights
Aquaculture is a promising sector of fish industry in the world with about 80 million tones being produced annually (Kolkovski and Kolkovski, 2011)
This work aimed to investigate the role of some immunostimulants and probiotics in improving the response of overwintered tilapia to Aeromonas hydrophila vaccine
A significant high value in the antibody titer was recognized in vaccinated overwintered tilapia at the end of 6th-8th week post-vaccination (PV) in the control group and between the 4th – 8th week PV in the immunostimulant supplemented groups (Groups 2-3), and between the 2nd – 10th week PV in probiotic supplemented groups (Groups 4 and 5)
Summary
Aquaculture is a promising sector of fish industry in the world with about 80 million tones being produced annually (Kolkovski and Kolkovski, 2011). Pose one of the most significant threat to successful fish production throughout the world (Rahman et al, 2009). In Egypt, bacterial diseases induce heavy mortality in farm fish (Aly, 2013). Winter season in Egypt stress tilapia causing low survival and render hatcheries unable to produce fry to stock in the ponds during winter which limit the length of the production season until June with a huge economic loss for the inability to use the fish farm during that period. The control of bacterial infection in fish is managed through the use of vaccines or via biological control using safe microorganisms (Aly et al, 2015; Aly and Mohamed, 2010)
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