Abstract
The simultaneous quantification of several transcripts via multiplex PCR can accelerate research in fish physiological responses to diet and enable the development of superior aquafeeds for farmed fish. We designed two multiplex PCR panels that included assays for 40 biomarker genes representing key aspects of fish physiology (growth, metabolism, oxidative stress, and inflammation) and 3 normalizer genes. We used both panels to assess the physiological effects of replacing fish meal and fish oil by terrestrial alternatives on Atlantic salmon smolts. In a 14-week trial, we tested three diets based on marine ingredients (MAR), animal by-products and vegetable oil (ABP), and plant protein and vegetable oil (VEG). Dietary treatments affected the expression of genes involved in hepatic glucose and lipid metabolism (e.g., srebp1, elovl2), cell redox status (e.g., txna, prdx1b), and inflammation (e.g., pgds, 5loxa). At the multivariate level, gene expression profiles were more divergent between fish fed the marine and terrestrial diets (MAR vs. ABP/VEG) than between the two terrestrial diets (ABP vs. VEG). Liver ARA was inversely related to glucose metabolism (gck)- and growth (igfbp-5b1, htra1b)-related biomarkers and hepatosomatic index. Liver DHA and EPA levels correlated negatively with elovl2, whereas ARA levels correlated positively with fadsd5. Lower hepatic EPA/ARA in ABP-fed fish correlated with the increased expression of biomarkers related to mitochondrial function (fabp3a), oxidative stress (txna, prdx1b), and inflammation (pgds, 5loxa). The analysis of hepatic biomarker gene expression via multiplex PCR revealed potential physiological impacts and nutrient-gene interactions in Atlantic salmon fed lower levels of marine-sourced nutrients.
Highlights
The future of farming of Atlantic salmon (Salmo salar) and other carnivorous fish lies in the utilization of aquafeeds with a minimum contribution from ingredients sourced in wild fishElectronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.stocks
The liver tissue samples utilized in the study were collected from Atlantic salmon smolts fed for 14 weeks with either a diet based on marine ingredients (i.e., fish meal (FM) and fish oil (FO)), referred to here as MAR; a high animal by-product/ high rapeseed oil diet, referred to as ABP; and a high plant protein/high rapeseed oil diet, referred to as vegetable oil (VEG)
The principal coordinates analysis (PCoA) of the resemblance among salmon based on the multiplex data explained 50.5% of the variation and separated ABP, VEG, and MAR-fed salmon—from the top left to the bottom right corner, respectively (Fig. 2)
Summary
Replacement of these marine products—namely, fish meal (FM) and fish oil (FO)—by different terrestrial alternatives has been investigated, with a particular focus on their impact on fish performance and chemical composition (Oliva-Teles et al 2015; Roques et al 2018). Growth on experimental feeds with low marine product inclusion has been similar to that with FM/FO-based aquafeeds (Lu et al 2015; Torrecillas et al 2017; Beheshti Foroutani et al 2018). The same studies reported significant changes in the chemical composition of the fish, which could affect the quality of the fish as a commodity. Omics in fish nutrition research has revealed profound metabolic and physiological adjustments occurring in fish fed diets based on terrestrial products (Sitjà-Bobadilla et al 2005; Tacchi et al 2012; Caballero-Solares et al 2018). The inclusion of plant proteins in the diet increased blood and liver redox status in gilthead sea
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