Dietary Buglossoides arvensis Oil as a Potential Candidate to Substitute Fish Oil in Rainbow Trout Diets

Abstract

The utilization of vegetable oils in salmonid diets substantially decreased the body content of omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA), and thus the product quality for human consumption. Therefore, new ingredients for aquaculture feeds are needed that maximize the deposition of health-promoting n-3 LC-PUFA. This study investigated Buglossoides arvensis (Ahiflower) oil, a plant oil rich in alpha-linolenic acid (18:3n-3, ALA) and stearidonic acid (18:4n-3, SDA), as a source of n-3 fatty acids in rainbow trout (Oncorhynchus mykiss) nutrition. Rainbow trout (87.4 AE 0.6 g) were fed for 56 days. The oils of the control diet (FV) were substituted by Ahiflower oil at 33%, 66%, and 100% (A33, A66, A100). Dietary Ahiflower oil increased the final body weights of fish. mRNA steady state levels of fatty acyl desaturase 2a (delta-6) (fads2a(d6)) and 2b (delta-5) (fads2b(d5)) as well as carnitine palmitoyl transferase 1 a (cpt1a) were not altered by dietary treatments. In contrast, cpt1c mRNA steady state levels were significantly downregulated in samples of fish fed A66 and A100. Significantly higher eicosapentaenoic acid (20:5n-3, EPA) and docosahexaenoic acid (22:6n-3, DHA) levels were found in the liver and significantly higher EPA levels in the fillet of rainbow trout of A66 and A100 compared to FV. The content of DHA in fillets of fish fed Ahiflower oil was not significantly different to fish fed FV. Thus, high dietary amounts of Ahiflower oil can compensate for reduced dietary EPA and DHA levels.Keywords Ahiflower oil Á Fatty-acid metabolism Á Longchain polyunsaturated fatty acids (LC-PUFA) Á Oil replacement Á Rainbow trout Á Stearidonic acid Lipids (2018) 53: 809-823.

Combination of Dietary Ahiflower Oil and Equol Enhances Long‐Chain Polyunsaturated Fatty Acid Levels in Rainbow Trout Tissues

“…Thus, it seems that the fatty acids ALA and SDA of the AV‐diets served as substrates for the biosynthesis of EPA and DHA without impairing fish growth. This is in line with findings of our previous study using different inclusion levels of Ahiflower oil in rainbow trout diets (Fickler et al, ). Furthermore, the results of the present study also confirm our previous study that equol (0.1–0.3% of DM in the diet) combined with vegetable oil‐based diets did not impair the growth of rainbow trout (submitted).…”

“…Specifically, the EPA and DHA liver levels were affected by the dietary treatments. The increased EPA levels in livers of fish fed the AV‐diets are in accordance with results of our previous study using Ahiflower oil in rainbow trout diets (Fickler et al, ). We assumed that high amounts of dietary SDA could bypass the initial delta‐6 desaturation step from ALA to SDA, thereby increasing the levels of EPA.…”

“…Thus, it seems that the fatty acids ALA and SDA of the AV-diets served as substrates for the biosynthesis of EPA and DHA without impairing fish growth. This is in line with findings of our previous study using different inclusion levels of Ahiflower oil in rainbow trout diets (Fickler et al, 2018). Furthermore, the results of the present study also confirm our previous study that equol Values (mean AE SD, n = 3, consisting of three fish each) with different superscript letters within one row are significantly different (p < 0.05), values without superscript letters within one row are not significantly different (p ≥ 0.05) based on the statistical models described in Materials and methods.…”

“…Dietary SDA has been shown to be more readily bionconverted to n‐3 LC‐PUFA than ALA in humans and rainbow trout (Cleveland et al, ; James et al, ; Kuhnt et al, ). In our previous study, we showed that dietary Ahiflower oil significantly increased the content of EPA in livers and fillets of rainbow trout in comparison to fish fed a diet based on a fish and vegetable oil (FV) blend (Fickler et al, ). This effect was putatively due to bypassing the first step in the biosynthesis of LC‐PUFA.…”

“…More than 50% of fish and aquatic plants for human consumption worldwide is supplied by aquaculture (FAO, 2015). One of the most cultured salmonids is rainbow trout (Oncorhynchus mykiss) (FAO, 2015) and farming this carnivorous fish species was responsible for a large use of fish oil (Tacon et al, 2011;Tacon and Metian, 2008). During the last few decades, fish oil production remained on a stable level (FAO, 2012) while aquaculture production increased rapidly (FAO, 2014).…”