Substitution of dietary fish oil with plant oils is associated with shortened mid intestinal folds in Atlantic salmon (Salmo salar)

Abstract

BackgroundFish meal and fish oil are increasingly replaced by ingredients from terrestrial sources in the feeds for farmed salmonids due to expanding production and reduced availability of marine feed raw material. Fish oil that is rich in n-3 polyunsaturated fatty acids is considered beneficial to human health in general and to prevent intestinal inflammation and carcinogenesis in particular. In contrast, n-6 fatty acids that are present in many vegetable oils have been associated with increased risk of colitis and colon cancer in rodents and humans, as well as lowered transcription levels of certain stress and antioxidant-related genes in Atlantic salmon.The aim of the present study was to investigate the intestinal health in Atlantic salmon fed with different vegetable oils as partial substitutes of fish oil in the diet. A feed trial lasting for 28 weeks included one reference diet containing fish oil as the sole lipid source and three diets where 80% of the fish oil was replaced by a plant oil blend with either olive oil, rapeseed oil or soybean oil as the main lipid source. These plant oils have intermediate or low n-3/n-6-ratios compared to fish oil having a high n-3/n-6-ratio. The protein and carbohydrate fractions were identical in all the feeds.ResultsMorphometric measurements showed significantly shorter folds in the mid intestine in all groups fed vegetable oils compared to the group fed fish oil. In the distal intestine, the complex folds were significantly shorter in the fish fed soybean oil compared to the fish fed rapeseed oil. Histological and immunohistochemical examination did not show clear difference in the degree of inflammation or proliferation of epithelial cells related to dietary groups, which was further confirmed by real-time RT-PCR which revealed only moderate alterations in the mRNA transcript levels of selected immune-related genes.ConclusionsShortened intestinal folds might be associated with reduced intestinal surface and impaired nutrient absorption and growth, but our results suggest that partial substitution of dietary fish oil with vegetable oils does not have any major negative impact on the intestinal health of Atlantic salmon.

Defatted Biomass of the Microalga, Desmodesmus sp., Can Replace Fishmeal in the Feeds for Atlantic salmon

“…In the present study, the mRNA levels of tgfb and il17d of the algal groups were similar to those of the control fish. The transcripts of il1b and tnfa were not altered in the intestine of Atlantic salmon fed olive oil, rapeseed oil or soybean oil (Moldal et al, 2014). However, soybean oil feeding was found to lower the igm and igt levels in the distal intestine of the fish (Moldal et al, 2014).…”

“…The transcripts of il1b and tnfa were not altered in the intestine of Atlantic salmon fed olive oil, rapeseed oil or soybean oil (Moldal et al, 2014). However, soybean oil feeding was found to lower the igm and igt levels in the distal intestine of the fish (Moldal et al, 2014). The feeding of the algal biomass in this study did not alter the level of igt in the distal intestine of Atlantic salmon.…”

Untitled

“…Intestinal folds and tunica mucosa contain connective tissue and blood vessels involving in nutritional absorption and immunological processes (Eurell & Frappier, 2006). Shortened intestinal folds might be associated with reduced intestinal surface and impaired nutrient absorption and growth, but previous reports have suggested that partial substitution of dietary fish oil with vegetable oils does not have any major negative impact on intestinal health of Atlantic salmon (Moldal et al, 2014). Tunica mucosa in CO group was thicker than FO group, nevertheless height and diameter of intestinal folds also increased predominantly in LO group.…”

“…Changes in dietary FA composition have been reported to affect FA composition of fish lipids storage and cell membranes in hepatic (Kjaer et al, 2008;Fountoulaki, Alexis, Nengas, & Venou, 2005;Castro et al, 2015), intestinal (Caballero et al, 2003;Ruyter, Moya-Falcón, Rosenlund, & Vegusdal, 2006) and digestive tract tissues (Olsen, Myklebust, Kaino, & Ringo, 1999;Moldal et al, 2014 of alpha-linolenic acid, accumulations of fat droplets in enterocytes of pyloric appendages and midgut were observed previously (Olsen, Myklebust, Ringo, & Mayhew, 2000). These changes in alimentary tract can accommodate transport and metabolism of fat in the body and decrease protein and fat digestion (Francis, Turchini, Jones, & De Silva, 2007).…”

Tench (Tinca tinca) high-throughput transcriptomics reveal feed dependent gut profiles

“…trypsin inhibitors, saponins) present in plant-based feeds (Knudsen et al, 2008). In the study published for S. salar, Moldal et al (2014) identified moderate alterations in the mRNA transcript levels of selected immune-related genes (e.g. CD3ζ, MHC class II) between all groups fed vegetable oils compared to the group fed fish oil.…”