Impact of plant-based oils and other feed ingredients on growth, tissue composition, gene expression, and health of Atlantic salmon (Salmo salar)

• Main Author: Katan, Tomer
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2022
• Subjects: Atlantic salmon; Salmo salar
• Online Access: https://research.library.mun.ca/15382/; https://research.library.mun.ca/15382/1/thesis.pdf

The ω6 to ω3 (ω6:ω3) fatty acid (FA) ratio is known to affect many biological processes (e.g. inflammation, FA metabolism) and human diseases. However, its impacts on salmon physiology, immune response, and the underlying molecular mechanisms are less well understood. The current thesis applied a nutrigenomics and lipidomics approach to study the impacts of plant-based feeds with varying dietary ω6:ω3 ratios and ω3 long chain polyunsaturated fatty acid (LC-PUFA) levels on farmed salmon growth, tissue composition and lipid metabolism, gene expression, and antibacterial immune response. In Chapter 2 Atlantic salmon were fed with diets containing the same sources and equal levels of marine and plant proteins, and differed in plant oil mixes to generate a range of ω6:ω3 (i.e. 0.3-2.7). A targeted qPCR study was used to measure the mRNA expression of lipid metabolism and eicosanoid synthesis-related genes in the liver. This study revealed that while growth performance and organ indices were not affected by dietary ω6:ω3, liver and muscle FA composition was highly reflective of the diet and suggested elongation and desaturation of 18:3ω3 and 18:2ω6. Compound-specific stable isotope analysis further demonstrated that liver 20:5ω3 and 20:4ω6 synthesis was largely driven by dietary 18:3ω3 and 18:2ω6, respectively. Moreover, significant correlations between LC-PUFA synthesis-related transcripts and liver LC-PUFA further supported FA biosynthesis. In Chapter 3, I used the same fish from the previous feeding trial in order to investigate how the two extreme ω6:ω3 diets (i.e. high ω6 and high ω3) affected the hepatic transcriptome (using 44K microarrays), and to identify novel biomarker genes that respond to variation in ω6:ω3. The microarray study identified transcripts with important roles in lipid metabolism (helz2a), cell proliferation (htra1b), immune and inflammatory response (lect2a, itgb5, helz2a, p43), control of muscle and neuronal cell development (mef2d), and translation (eif2a, eif4b1, p43). Further, the PPARα ...