Abstract
Decline in fish oil and fish meal availability has forced the aquaculture sector to investigate alternative and sustainable aquafeed ingredients. Despite that several studies have evaluated the effect of fish oil replacement in aquaculture fish species, there is a knowledge gap on the effects of alternative dietary lipid sources on the gut microbiota in early life stages of Salmo salar. The present study evaluated the influence of dietary administration of two different lipid sources (fish oil and vegetable oil) on the intestinal microbiota of first feeding Atlantic salmon (S. salar) up to 93 days post first feeding (dpff). The two diets used in this study, FD (fish oil diet) and VD (blend of rapeseed, linseed and palm oils diet), were formulated to cover the fish nutritional requirements. Apart from the lipid source, the rest of the feed components were identical in the two diets. Hindgut samples were collected at 0, 35, 65, and 93 dpff. Moreover, fertilized eggs, yolk sac larvae, rearing water and feed were also collected in order to assess a possible contribution of their microbiota to the colonization and bacterial succession of the fish intestines. To analyze the bacterial communities, amplicon sequencing was used targeting the V3–V4 region of the 16S rRNA gene. The findings indicate that feeding on either fish oil or vegetable oil-based diet, fish growth variables (mean wet weight and total length) did not differ significantly during the experiment (p > 0.05). No significant differences were also found between the two dietary groups, regarding their gut bacteria composition, after the analysis of the 16S rRNA sequencing data. Instead, gut microbiota changed with age, and each stage was characterized by different dominant bacteria. These operational taxonomic units (OTUs) were related to species that provide different functions and have been isolated from a variety of environments. The results also show little OTUs overlap between the host and rearing environment microbiota. Overall, this study revealed the occurrence of a core microbiota in early life of Atlantic salmon independent of the feed-contained oil origin.
Highlights
Fishmeal and fish oil have been the main ingredients in diets for farmed carnivorous fish species, providing the fed fish with the necessary proteins and lipids for high growth performance and resulting in a nutritionally rich final product (International Fishmeal and Oil Manufacturers Association [IFOMA], 2001; Turchini et al, 2010)
The analysis of the 16S rRNA sequencing data revealed a total of 4,548 unique operational taxonomic units (OTUs), with the rarefaction curves (Supplementary Figure 2) and the OTUs richness coverage based on the Chao1 index (Supplementary Table 5) indicating satisfactory sequencing depth
The present study evaluated the effect of total fish oil replacement by a blend of terrestrial vegetable oils in the feed on the colonization and the bacterial succession in first feeding of Atlantic salmon, up to 93 days dpff
Summary
Fishmeal and fish oil have been the main ingredients in diets for farmed carnivorous fish species, providing the fed fish with the necessary proteins and lipids for high growth performance and resulting in a nutritionally rich final product (International Fishmeal and Oil Manufacturers Association [IFOMA], 2001; Turchini et al, 2010). In Atlantic salmon (S. salar), a carnivorous fish with significant economic value in European aquaculture (FAO, 2004), the effect of the alternative aquafeed ingredients on the gut microbiota have been evaluated previously and, in some cases, it was revealed that changes associated with intestinal disorders and slower growth performance, were related to the fishmeal diets (e.g., Green et al, 2013; Navarrete et al, 2013; Schmidt et al, 2016; Gajardo et al, 2017; Booman et al, 2018; Egerton et al, 2020) These studies, have focused mainly on alternative protein sources and on juveniles and adult stages. In a different salmonid species (rainbow trout), gut microbiota was detectable before first feeding commenced, potentially due to contact with the surrounding water and yok sac digestion, indicating that gut microbiota establishment initiates at first feeding and that diet-type affect the bacterial composition (Ingerslev et al, 2014a,b)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
