PhD defence and trial lecture: Nimalan Nadanasabesan

Thesis title​​​:

Dietary approaches to improve mucosal health of Atlantic salmon (Salmo salar)

Trial lecture topic:

Current tools in assessing efficacy of pre-, pro-, and postbiotic use in farmed teleosts

Evaluation Committee​:

• Professor Efthimia Antonopoulou, Aristotle University of Thessaloniki, Faculty of Sciences, Department of Zoology, Laboratory of Animal Physiology, Greece
• Researcher Elvis Chikwati, Aquamedic AS, Oslo
• Associate Professor Hetron Mweemba Munang'andu, Nord University

Supervisory Committee:

• Main supervisor: Professor Mette Sørensen, Nord University
• Co-supervisor: Associate Professor Ioannis Vatsos, Nord University
• Co-supervisor: Professor Kiron Viswanath, Nord University
  

About the thesis:

The mucosal surfaces are efficient defense sites of fishes, and these barriers have important physiological and immune functions. Plant-based ingredients can compromise the health of Atlantic salmon and hence, different feed additives or novel ingredients can be exploited to improve the health of mucosal surfaces. The current salmon feeds contain ingredients from legumes that have antinutritional factors including saponins. These compounds are known to impart adverse effects on nutrient digestion, utilization, and health of Atlantic salmon.

In the present thesis, experiments were conducted to investigate the ability of probiotics, Ca-butyrate, and microalgae to improve the mucosal health of salmon fed marine- or plant-based diets. The results revealed that mucosal health of the fish fed marine-based diet was better than those fed plant-based diets. The findings indicated that lactic acid bacteria or Ca-butyrate can be used to improve mucosal health i.e., to prevent the soybean meal or soyasaponin-induced enteritis. Feed additives improved the intestine micromorphological features, by preserving the villi and enterocyte height, and supranuclear vacuoles in the enterocytes. Inclusion of microalgae such as Nannochloropsis sp. (7.5% of the feed), in plant-based diets also improved the mucosal health.

This research adds new knowledge to the understanding of the interplay between certain ingredients/additives in salmon feeds and mucosal health of salmon. The findings are expected to bolster the sustainability aspect of the Atlantic salmon aquaculture in Norway.