Long Term Study of Nutritionally Stimulated Atlantic Salmon (Salmo salar L.) from Different Pigment Deposition Genotypes

The rapid expansion of the Atlantic salmon (Salmo salar L.) farming industry, combined with the growing shift from traditional fish meal and fish oil to alternative ingredients, highlights the need for novel approaches to equip fish with the necessary tools to adapt successfully to newly formulated diets. Nutritional programming refers to a phenomenon where exposure to a specific stimulus during a critical developmental window results in lasting alterations in structures or functions. Although previous studies have shown that a dietary stimulus can influence fish growth and metabolism through both direct (alevin) and indirect (broodstock) pathways in Atlantic salmon, the underlying mechanisms and the extent of these effects throughout the productive life cycle require further investigation. This thesis examines the progression of using either a marine- or a vegetable-based diet as nutritional stimulus, and their impact when fish are later challenged with a vegetable-origin feed in seawater, plus dietary interaction with fish genotype characterized by low and high pigment deposition. Chapter 3 examined the effects of stimulus diet, genotype, and their interaction on survival, growth, feed utilization, and the chemical composition of feed, whole fish and tissues throughout the trial. Chapter 4 assessed the lipid and fatty acid composition of liver and intestine at post-smolt sampling times, analysed their histomorphology, and studied the expression of genes related to the metabolism of long-chain polyunsaturated fatty acids in liver before and after the challenge phase. Chapter 5 analysed the methylation patterns in liver throughout the trial, identifying differentially methylated sites based on dietary stimulus or genotype, and assessed their functional enrichment and possible implications. Overall, the results of this study offer valuable insights into the long-term effects of nutritional strategies using vegetable-based diets for Atlantic salmon from different genotype.