Influence of Dietary LC-PUFA on Atlantic Salmon Growth and the Hepatic Transcriptome

The minimal requirement of ω3 long-chain polyunsaturated fatty acids (ω3 LC-PUFA), namely docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), for Atlantic salmon warrants careful investigation. We studied the influence of increasing levels of dietary DHA and EPA (0, 1 and 1.4% of the diet as formulated) on Atlantic salmon performance. After a 14-week feeding trial, Atlantic salmon fed diet ω3LC0 (i.e. 0% of DHA and EPA) showed significantly lower final weight and weight gain compared to those fed ω3LC1 and ω3LC1.4 diets. A 44K microarray experiment was conducted to investigate the liver transcriptome response of fish fed these three dietary groups. Rank Products analysis (PFP<10%) showed that 55 and 77 differentially expressed microarray features were identified in salmon fed diets ω3LC1.4 and ω3LC1 compared with those fed diet ω3LC0, respectively. The comparison between ω3LC1.4 and ω3LC1 revealed 134 differentially expressed features. Twenty-one microarray-identified genes were subjected to qPCR validation. Seven of these transcripts (33%), namely fadsd5, fas2, mgst1, glrx1, pdk2, lect-2a and lysc2, were shown by qPCR to be significantly affected by dietary DHA and EPA; eleven of the remaining transcripts studied by qPCR agreed with the microarray results in direction of change (i.e. up- or down-regulation). Interestingly the expression of three well-known anti-viral genes (irf3, mxb and itif5) all showed consistent down-regulation trends (not significant) in fish fed ω3LC1.4 compared with fish fed both diets with lower dietary DHA and EPA. This research has provided new insights into the influence of dietary DHA and EPA on Atlantic salmon growth performance, metabolism and health.