Reflecting the natural biology of mass spawning fish aquaculture production of fish larvae is often
hampered by high and unpredictable mortality rates. The present study aimed to enhance larval performance
and immunity via the oral administration of an immunomodulator, b-glucan (MacroGard®) in
turbot (Scophthalmus maximus). Rotifers (Brachionus plicatilis) were incubated with or without yeast b-
1,3/1,6-glucan in form of MacroGard® at a concentration of 0.5 g/L. Rotifers were fed to first feeding
turbot larvae once a day. From day 13 dph onwards all tanks were additionally fed untreated Artemia sp.
nauplii (1 nauplius ml/L). Daily mortality was monitored and larvae were sampled at 11 and 24 dph for
expression of 30 genes, microbiota analysis, trypsin activity and size measurements. Along with the
feeding of b-glucan daily mortality was significantly reduced by ca. 15% and an alteration of the larval
microbiota was observed. At 11 dph gene expression of trypsin and chymotrypsin was elevated in the
MacroGard® fed fish, which resulted in heightened tryptic enzyme activity. No effect on genes encoding
antioxidative proteins was observed, whilst the immune response was clearly modulated by b-glucan. At
11 dph complement component c3 was elevated whilst cytokines, antimicrobial peptides, toll like receptor
3 and heat shock protein 70 were not affected. At the later time point (24 dph) an antiinflammatory
effect in form of a down-regulation of hsp 70, tnf-a and il-1b was observed. We
conclude that the administration of MacroGard® induced an immunomodulatory response and could be
used as an effective measure to increase survival in rearing of turbot.
Reflecting the natural biology of mass spawning fish aquaculture production of fish larvae is oftenhampered by high and unpredictable mortality rates. The present study aimed to enhance larval performanceand immunity via the oral administration of an immunomodulator, b-glucan (MacroGard®) inturbot (Scophthalmus maximus). Rotifers (Brachionus plicatilis) were incubated with or without yeast b-1,3/1,6-glucan in form of MacroGard® at a concentration of 0.5 g/L. Rotifers were fed to first feedingturbot larvae once a day. From day 13 dph onwards all tanks were additionally fed untreated Artemia sp.nauplii (1 nauplius ml/L). Daily mortality was monitored and larvae were sampled at 11 and 24 dph forexpression of 30 genes, microbiota analysis, trypsin activity and size measurements. Along with thefeeding of b-glucan daily mortality was significantly reduced by ca. 15% and an alteration of the larvalmicrobiota was observed. At 11 dph gene expression of trypsin and chymotrypsin was elevated in theMacroGard® fed fish, which resulted in heightened tryptic enzyme activity. No effect on genes encodingantioxidative proteins was observed, whilst the immune response was clearly modulated by b-glucan. At11 dph complement component c3 was elevated whilst cytokines, antimicrobial peptides, toll like receptor3 and heat shock protein 70 were not affected. At the later time point (24 dph) an antiinflammatoryeffect in form of a down-regulation of hsp 70, tnf-a and il-1b was observed. Weconclude that the administration of MacroGard® induced an immunomodulatory response and could beused as an effective measure to increase survival in rearing of turbot.
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