Immunogenicity and growth response of Atlantic salmon to the addition of marine diatom, Skeletonema Marinoni as a functional feed ingredient

Authors: MEESALA, KALA - University Of Maine; JANSON, SARAH - University Of Maine; HONG, JEONGWHUI - University Of Maine; SULLIVAN, ALEX - University Of Maine; Polinski, Mark; Burr, Gary; LOMAS, MICHAEL - Bigelow Laboratory For Ocean Sciences; BOUCHARD, DEBORAH - University Of Maine; HABTE-TSION, MICHAEL - University Of Maine

Submitted to: Aquaculture America Conference
Publication Type: Abstract Only
Publication Acceptance Date: 2/18/2024
Publication Date: 2/18/2024
Citation: Meesala, K.M., Janson, S., Hong, J., Sullivan, A., Polinski, M.P., Burr, G.S., Lomas, M., Bouchard, D., Habte-Tsion, M. 2024. Immunogenicity and growth response of Atlantic salmon to the addition of marine diatom, Skeletonema Marinoni as a functional feed ingredient (abstract). Aquaculture America Conference. 02182024.

Interpretive Summary: Atlantic salmon (Salmo salar) is one of the most commercially farmed aquaculture species in the world. Functional feed ingredients with antimicrobial activities are being explored as a tool to mitigate disease and the marine diatom, Skeletonema marinoi is known to have antimicrobial activity. Here we study the effects of dietary Skeletonema marinoi on the growth, health, and immunogenicity of Atlantic salmon. Two separate experiments were conducted: a bacterial challenge and a growth study. Following a 28 day cohabitation bacterial challenge using a Vibrio anguillarum S03 strain, salmon fed the antimicrobial algal diet showed significantly higher liver oxidation levels on day 5 post-bacterial challenge and intestinal immunoglobulin (IgM) gene expression was significantly higher in fish fed skeletonema marinoi diets (P< 0.05) at 28 days post challenge. These data suggest that the addition of the diatom, Skeletonema marinoi in feed may enhance the salmon immune response. In a separate 16 week growth trial experiment, there was no significance difference in survival, weight gain, feed conversion ratio, hepatosomatic index, and condition factor between fish fed with Skeletonema marinoi diet and the commercial diet, suggesting general growth performance of cultured salmon was uncompromised by the addition of algae to the feed.

Technical Abstract: Atlantic salmon (Salmo salar) is one of the most commercially farmed aquaculture species in the world. As with all cultured species, disease can be a major impediment to production activities. Functional feed ingredients with antimicrobial activities are being explored as a tool to mitigate disease and the marine diatom, Skeletonema marinoi is known to have antimicrobial activity. Here we study the effects of dietary Skeletonema marinoi on the growth, health, and immunogenicity of Atlantic salmon. Two separate experiments were conducted: a bacterial challenge (Exp.1) and a growth study (Exp.2). In Exp.1, a 28-day bacterial challenge using Vibrio anguillarum S03, the causative agent of Vibriosis, was conducted at the University of Maine, Aquaculture Research Institute. Thirty-six fish (100-150g/fish) were stocked into each tank (150 liters), brackish water (18 ppt) at 14' in recirculatory aquaculture systems (RAS). Fish were acclimatized to the RAS system for 14 days by feeding twice a day, one group was fed with 0.5% diatom, Skeletonema marinoi top-coated on a commercial diet, and the other group was fed with a commercial diet in triplicate. The liver, blood plasma, and intestine samplings were collected before (initial 0 days) and post-challenge (5, 10, 28 days) to assess the effect of the addition of the diatom in feed on the immune response in Atlantic salmon exposed to a bacterial challenge. In Exp 2. a 16-week growth trial was conducted at the USDA-ARS National Cold Water Marine Aquaculture Center, Franklin, Maine. Ten fish were stocked into each tank with replicates of five tanks per treatment and fed twice a day. The growth trial involved two treatments: a reference diet and the reference diet supplemented with 0.5% Skeletonema marinoi diet. According to the bacterial challenge results, salmon fed the antimicrobial algal diet showed significantly higher liver oxidation levels on day 5 post-bacterial challenge but not at 10- and 28-days post-challenge compared to salmon fed a standard commercial diet. By 28 days post challenge, intestinal immunoglobulin (IgM) gene expression was significantly higher in fish fed skeletonema marinoi diets (P< 0.05). These data suggest that the addition of the diatom, Skeletonema marinoi in feed may enhance the salmon immune response. In Exp 2., there was no significance difference in survival, weight gain, feed conversion ratio, hepatosomatic index, and condition factor between fish fed with the 0.5% Skeletonema marinoi diet and the reference diet, suggesting general growth performance of cultured salmon was uncompromised by the addition of algae to the feed. Results of additional measured parameters from these experiments will be discussed.