Effects of dietary linseed oil on innate immune system of Eurasian perch and disease resistance after exposure to Aeromonas salmonicida achromogen.
This study was designated to investigate the effects of dietary fish oil (FO diet) replacement by linseed oil (LO diet) on regulation of immune response and disease resistance in Eurasian perch (Perca fluviatilis). A control diet containing fish oil (FO = cod liver oil) and characterized by high levels of n-3 high LC-PUFA (6% EPA, 7.5% of total fatty acids (FAs)) was compared to linseed oil diet (LO diet) composed of low LC-PUFA contents (1% EPA, 2.3% DHA of total FAs) but high C18 fatty acids levels. The experiment was conducted in quadruplicate groups of 80 fish each. After 10 weeks of feeding, the innate immune status was evaluated in various organs (liver, spleen, and head-kidney) (feeding condition). Two days later, a bacterial challenge was performed on fish from 2 rearing conditions: fish infected with Aeromonas salmonicida (bacteria condition) and fish injected with sterile medium but maintained in the same flow system that fish challenged with bacteria (sentinel condition). Three days after injection of bacteria, a significant decrease of lymphocyte, thrombocyte and basophil populations was observed while neutrophils were not affected. In addition, plasma lysozyme activity and reactive oxygen species production in kidney significantly increased in fish challenged with A. salmonicida while the plasma alternative complement pathway activity was not affected. Increase of plasma lysozyme activity as well as reactive oxygen species production in spleen and kidney of sentinel fish suggest that these immune defenses can also be activated, but at lower bacteria concentration than infected fish. No differences in leucocyte populations, plasma lysozyme and alternative complement pathway activities were observed between dietary treatments. Similarly, expression of genes related to eicosanoid synthesis in liver were not affected by the dietary oil source but were strongly stimulated in fish challenged with A. salmonicida. These findings demonstrated that the use of linseed oil does not deplete the innate immune system of Eurasian perch juveniles.
Research Unit of Environmental and Evolutionary Biology (URBE), University of Namur (UNamur), Rue de Bruxelles, 61, 5000 Namur, Belgium.
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Geay
Institut des Sciences de la Vie, Université catholique de Louvain, Croix du Sud, 2/L7.05.08, 1348 Louvain-la-Neuve, Belgium.
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Mellery
Unité de Chimie Physique Théorique et Structurale, Université de Namur (UNamur), Rue de Bruxelles 61, 5000 Namur, Belgium.
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Tinti
Research Unit of Environmental and Evolutionary Biology (URBE), University of Namur (UNamur), Rue de Bruxelles, 61, 5000 Namur, Belgium.
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Douxfils
Institut des Sciences de la Vie, Université catholique de Louvain, Croix du Sud, 2/L7.05.08, 1348 Louvain-la-Neuve, Belgium.
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Larondelle
Research Unit of Environmental and Evolutionary Biology (URBE), University of Namur (UNamur), Rue de Bruxelles, 61, 5000 Namur, Belgium.
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Mandiki
Research Unit of Environmental and Evolutionary Biology (URBE), University of Namur (UNamur), Rue de Bruxelles, 61, 5000 Namur, Belgium. Electronic address: patrick.kestemont@unamur.be.
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Kestemont
D048409:Aeromonas salmonicida / Q000502:physiology; D000821:Animal Feed / Q000032:analysis; D000818:Animals; D004032:Diet / Q000662:veterinary; D004042:Dietary Fats, Unsaturated / Q000494:pharmacology*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D005393:Fish Diseases / Q000276:immunology* / Q000382:microbiology; D015870:Gene Expression; D016905:Gram-Negative Bacterial Infections / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D007113:Immunity, Innate; D008043:Linseed Oil / Q000494:pharmacology*; D010471:Perches; D013997:Time Factors
D004042:Dietary Fats, Unsaturated; D005231:Fatty Acids, Unsaturated; D008043:Linseed Oil
Aeromonas salmonicida; Alternative complement pathway; Eicosanoid; Eurasian perch; Innate immune system; LC-PUFA; Linseed oil; Lysozyme; Reactive oxygen species