Evaluating the Effects of Dietary Prebiotic Mixture of Mannan Oligosaccharide and Poly‐β‐Hydroxybutyrate on the Growth Performance, Immunity, and Survival of Rainbow Trout, Oncorhynchus mykiss (Walbaum 1792), Fingerlings

Abstract

This study investigated the effects of dietary poly‐β‐hydroxybutyrate (PHB) and mannan oligosaccharide (MOS) on the growth performance, digestive enzyme activities, and disease resistance of rainbow trout fingerlings. A total of 420 fingerlings, distributed equally into four different groups, each with three replicates, were fed a basal diet (control), 2% PHB (PHB), 0.2% MOS (MOS), or a diet supplemented with a mixture of 2% PHB and 0.2% MOS (PHB+MOS) for 60 d. Results showed that dietary PHB and/or MOS did not cause significant improvement in the growth performance of the fingerlings. The gut pH was markedly reduced; however, the activities of the digestive enzymes (except for pepsin and amylase by dietary PHB) were not significantly improved by the dietary supplements. Results also showed that dietary PHB and/or MOS markedly increased the resistance of the fingerlings toward Yersinia ruckeri infection, while the lowest total antibody was observed in fish fed control and MOS, indicating that MOS exerts its protective effects by modulating other mechanisms. Overall, this study provided a first screening effort to determine the effects of PHB and/or MOS as dietary supplements in rainbow trout fingerlings to develop an optimal prebiotic mix for improving the growth and health status of rainbow trout.

Effects of Mannan Oligosaccharides on Gas Emission, Protein and Energy Utilization, and Fasting Metabolism in Sheep

“…MOS are found in the outer layer of yeast, Saccharomyces cerevisiae , in the cell wall. As the most bioactive compounds, they contain both mannan proteins and complex carbohydrates, including β-glucans [4], and are widely used as a dietary supplement to boost the immune system and eliminate pathogens from the intestinal tract [5,6]. For instance, MOS bind to the mannose-specific lectin of Gram-negative pathogens that express Type-1 fimbriae (e.g., Escherichia coli ), resulting in their excretion from the intestine [7].…”

The effects of dietary poly‐β‐hydroxybutyrate on growth parameters, intestinal microflora, and histopathology of rainbow trout, Oncorhynchus mykiss, fingerlings

“…Consequently, PHB is found to be ineffective for survival rates of rainbow trout fry in this experiment. Najdegerami et al (2017) reported a confirmatory effect of the PHB on rainbow trout fingerlings in their research as well. Another similar result was also expressed in an experiment with European sea bass post‐larvae, in which Franke, Clemmesen, et al (2017) fed the fish with PHB‐enriched Artemia nauplii and reported that the PHB did not affect the survival rates of the animals.…”

“…Considering the data obtained, PHB has been found not to affect the growth and survival rates of rainbow trout fry in this trial ( p > .05). In a similar study, Najdegerami et al (2017) investigated the effects of dietary PHB (2%), mannan‐oligosaccharide (MOS) (0.2%), and their mixture (2% PHB + 0.2% MOS) on rainbow trout fingerlings; and found neither positive nor negative changes in the growth and survival parameters of fish as well. Literature reports that the dietary PHB is known not to affect the growth performance of blue mussel larvae (Van Hung et al, 2015), while it adversely affects the growth performance of Siberian sturgeon larvae (Najdegerami et al, 2015).…”

“…Such effect of the PHB polymers is explained by researchers, as it degrades into short‐chain fatty acid oligomers and monomers, it could then decrease the intestinal pH of the investigated organism and improve the activity of the digestive enzymes, and provide better nutrient absorption. Alternatively, the monomers and oligomers of the PHB might act as additional energy source itself (Azain, 2004; Baruah et al, 2005, 2007; De Schryver et al, 2010; Defoirdt, Boon, Sorgeloos, Verstraete, & Bossier, 2009; Lückstädt, 2008; Najdegerami et al, 2012, 2017; Sui et al, 2012; Weltzien, Hemre, Evjemo, Olsen, & Fyhn, 2000). According to Najdegerami et al (2017), despite the necessary pH level and enzyme activities for degradation of PHB was achieved, the growth and survival parameters were not affected as expected.…”

“…Considering its beneficial effects on the intestinal microflora of the organism, PHB has been found to increase weight gain, survival, specific growth rate, and short‐chain fatty acid concentration in the gastrointestinal tract of certain aquaculture species such as European sea bass ( Dicentrarchus labrax ), Siberian sturgeon ( Acipenser baerii ), and giant river prawn larvae ( Macrobrachium rosenbergii ) (De Schryver et al, 2010; Najdegerami et al, 2012; Nhan et al, 2010). It also has protective efficacy on Artemia franciscana nauplii against vibriosis (Baruah et al, 2015; Defoirdt et al, 2007; Halet et al, 2007; Van Cam et al, 2009) and rainbow trout fry ( Oncorhynchus mykiss ) against Yersinia ruckeri (Najdegerami, Tokmachi, & Bakhshi, 2017). Moreover, bio‐encapsulated PHB into Rotifer and Artemia has also been shown to be effective on increased survival, development rate, and osmotic tolerance of Chinese mitten crab ( Eriocheir sinensis) zoea larvae (Sui et al, 2014).…”