title: Effect of a phytogenic feed additive on the susceptibility of Onchorhynchus mykiss to Aeromonas salmonicida.
abstract: In recent years, feed additives have increasingly been adopted by the aquaculture industry. These supplements not only offer an alternative to antibiotics but have also been linked to enhanced growth performance. However, the literature is still limited and provides contradictory information on their effectiveness. This is mainly due to the wide variety of available products and their complex mechanisms of action. Phytogenic feed additives have been shown to have antimicrobial effects and can improve growth performance. In the present study, we investigated the susceptibility of several fish pathogenic bacteria to a phytogenic essential oil product in vitro. In addition, we determined the protective effect of a commercial phytogenic feed additive containing oregano, anis and citrus oils on the resistance of rainbow trout Oncorhynchus mykiss to infection by Aeromonas salmonicida. The bacterium was administered through 3 different routes: intra-peritoneal injection, immersion in a bacterial solution and cohabitation with infected fish. Mortality rates were significantly lower in infected rainbow trout that had received the feed additive: the overall mortality rate across all routes of infection was 18% in fish fed a diet containing the additive compared to 37% in fish that received unsupplemented feed. The route of infection also significantly impacted mortality, with average mortality rates of 60, 17.5 and 5% for intra-peritoneal injection, immersion and cohabitation, respectively. In general, fish were better protected against infection by immersion than infection by injection.
authors.affiliation: Clinical Division of Fish Medicine, University of Veterinary Medicine, Vienna, Austria.
authors.forename: S
authors.initials: S
authors.lastname: Menanteau-Ledouble
authors.forename: I
authors.initials: I
authors.lastname: Krauss
authors.forename: G
authors.initials: G
authors.lastname: Santos
authors.forename: S
authors.initials: S
authors.lastname: Fibi
authors.forename: B
authors.initials: B
authors.lastname: Weber
authors.forename: M
authors.initials: M
authors.lastname: El-Matbouli
mesh_terms: D048409:Aeromonas salmonicida / Q000187:drug effects*; D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002701:Chloramphenicol / Q000494:pharmacology; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D024881:Drug Resistance, Bacterial; D005393:Fish Diseases / Q000188:drug therapy / Q000382:microbiology / Q000517:prevention & control*; D005503:Food Additives; D016905:Gram-Negative Bacterial Infections / Q000188:drug therapy / Q000382:microbiology / Q000517:prevention & control / Q000662:veterinary*; D009822:Oils, Volatile / Q000737:chemistry / Q000494:pharmacology; D017686:Oncorhynchus mykiss; D010118:Oxytetracycline / Q000494:pharmacology; D010938:Plant Oils / Q000737:chemistry / Q000494:pharmacology; D013047:Specific Pathogen-Free Organisms
chemical_list: D000900:Anti-Bacterial Agents; D005503:Food Additives; D009822:Oils, Volatile; D010938:Plant Oils; D002701:Chloramphenicol; D010118:Oxytetracycline