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2025-12-30 08:31 本頁(yè)面
【正文】 ? Usually added in feed or to culture water as preventative agents against infection by pathogenic bacteria ? Nutritional benefits are usually secondary ? Typical genera: Lactobacillus, Vibrio, Bacillus, Pseudomonas ? The following is a summary of findings based on various aquatic species Recent Findings: fish eggs/larvae ? For incubators, use of antibiotics must be minimal ? Antibiotics don’t represent control。 – 4) enhancing host response to disease (acquired)。Lecture Outline ? Introduction/Definition of Probiotics ? Fundamental Questions ? Recent Findings ? Possible Modes of Action ? Rationale for Selecting Probiotics ? Conclusions and Further Directions Source of notes: Verschuere, L., Rombaut, G., Seloos, P., and Verstraete, W., 2022. Probiotic bacteria as biological control agents in aquaculture. Microb. Mol. Biol. Rev., 64(4):655671. Introduction ? As we know, aquaculture is growing faster than beef cattle production (10% vs. 3%) ? Epizootics (disease) = major limiting factor in fish/shrimp developments! ? Disinfectants, antimicrobial drugs have had little effect in controlling disease. ? Massive use of antimicrobials increases selective pressure on microbes and encourages natural emergence of bacterial resistance ? Resistant bacteria thrive after nonresistant strains have been killed and can even pass on resistance genes to other bacteria that have not been exposed to antibiotics Introduction ? Emphasis should be place on prevention ? More costeffective than cure! ? Antimicrobials, disinfectants and pesticides largely treat symptoms of the problem and not the cause ? Alternative strategies are just catching on ? Example: via vaccination, Norway has reduced chemical therapeutant use from 50 MT in 1987 to less than 747 kg in 1997 (with 7x conitant production increase!) ? Other: use of immunostimulants w/or w/out vaccines Introduction ? Use of bacteria as a food source and as a biological control agent of fish disease was first proposed by Yasuda and Taga (1980) ? Vibrio alginolyticus has been used as a probiotic in shrimp hatcheries in Ecuador since 1992 ? Reduced hatchery down time from 7 days per month to less than 21 days per year! ? FAO has now designated use of probiotics as a major means for improvement of aquatic environmental quality ? Ultimate goal: make aquaculture products more acceptable to consumers Definition of Probiotics ? Many proposed, however: a live microbial feed supplement which beneficially affects the host animal by improving its intestinal balance ? Historically: terrestrial animals, genus Lactobacillus ? Definition (above) requires some additional considerations: – 1) bacteria in aquatic medium influence position of gut microbiota and vice versa – 2) immediate ambient environment has much greater influence on microbiota than with terrestrials ? In aquatic environments, hosts and microanisms share the ecosystem ? Terrestrials: the gut represents a moist habitat in a waterlimited world Definition of Probiotics ? Big Issue 1: aquatics are surrounded by an environment supporting their pathogens independently of the host animal
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