Abstract
The inclusion of macroalgae in the diets of farmed fish offers the opportunity for an added-value dietary ingredient to the nutraceutical feed. The composition of algae varies greatly among species. Several Ulva species have been considered in aquafeed formulations for different farmed fish, and Ulva ohnoi is being applied recently. However, the effects of seaweed dietary inclusion on the host must be evaluated. Considering the important role of the host intestinal microbiota, the potential effects of U. ohnoi dietary inclusion need to be studied. In this study, the characterization of the intestinal microbiome of Solea senegalensis, a flatfish with high potential for aquaculture in South Europe, receiving U. ohnoi (5%)-supplemented diet for 90 days has been carried out. In addition, the functional profiles of bacterial communities have been determined by using PICRUSt, a computational approach to predict the functional composition of a metagenome by using marker gene data and a database of reference genomes. The results show that long-term dietary administration of U. ohnoi (5%)-supplemented feed modulates S. senegalensis intestinal microbiota, especially in the posterior intestinal section. Increased relative abundance of Vibrio jointly with decreased Stenotrophomonas genus has been detected in fish receiving Ulva diet compared to control-fed fish. The influence of the diet on the intestinal functionality of S. senegalensis has been studied for the first time. Changes in bacterial composition were accompanied by differences in predicted microbiota functionality. Increased abundance of predicted genes involved in xenobiotic biodegradation and metabolism were observed in the microbiota when U. ohnoi diet was used. On the contrary, predicted percentages of genes associated to penicillin and cephalosporin biosynthesis as well as beta-lactam resistance were reduced after feeding with Ulva diet.
Highlights
Macroalgae have been widely evaluated as a novel ingredient for aquafeed formulation in recent years (Guerreiro et al, 2019; Wang et al, 2019; Yeganeh and Adel, 2019; Naylor et al, 2021)
Ulva species are a good source of protein, minerals, and vitamins, especially vitamin C (Ortiz et al, 2006; García-Casal et al, 2007), and different studies aimed at assessing the dietary inclusion of Ulva in a wide range of farmed fish species have been carried out (Wassef et al, 2013; Silva et al, 2015; Valente et al, 2016; Vizcaíno et al, 2016; Magnoni et al, 2017; Kazemi et al, 2018) with positive results on growth performance, innate immune response, feed utilization and overall fish health status
Significant decreased final body weight and weight gain rate values were obtained for fish fed with U. ohnoi 5%-supplemented diet; no differences in Feed conversion ratio (FCR) were detected based on the diet supplied
Summary
Macroalgae have been widely evaluated as a novel ingredient for aquafeed formulation in recent years (Guerreiro et al, 2019; Wang et al, 2019; Yeganeh and Adel, 2019; Naylor et al, 2021). The effects detected were dose-dependent and species-specific (Valente et al, 2006) In this context, Ulva species are a good source of protein, minerals, and vitamins, especially vitamin C (Ortiz et al, 2006; García-Casal et al, 2007), and different studies aimed at assessing the dietary inclusion of Ulva in a wide range of farmed fish species have been carried out (Wassef et al, 2013; Silva et al, 2015; Valente et al, 2016; Vizcaíno et al, 2016; Magnoni et al, 2017; Kazemi et al, 2018) with positive results on growth performance, innate immune response, feed utilization and overall fish health status. On the contrary, when added to fish diet at low percentages, benefits such as improved growth, feed efficiency, nutrient utilization, modulation of immune response, and disease resistance have been described in several fish species (Mustafa and Nakagawa, 1995; Wassef et al, 2005; Valente et al, 2006; Ergün et al, 2009; Moutinho et al, 2018; Fumanal et al, 2020)
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