Abstract
The application of β-1,3/1,6-glucan derived from yeast at five concentrations (0%, 0.5%, 1.0%, 1.5%, and 2.0%) in formulated diets was evaluated in juveniles for its effects on the growth, survival, digestive enzymatic activity, and expression of genes associated with the immune system (interlukin-10 (IL-10), transforming growth factor (TGF), occludin (OCC), mucin2 (MUC2), lysozyme (LYS), and nucleotide-binding and oligomerization domain 2 (NOD2)) in tropical gar (Atractosteus tropicus). For the experiment, three replicates of 30 fish per experimental unit (70 L) were cultivated for 62 days. The growth results showed no statistically significant differences in relation to weight and total length between treatments. The activity of digestive enzymes (alkaline proteases, trypsin, leucine aminopeptidase, and amylase) did not show significant differences between treatments, except for chymotrypsin activity, where fish fed 1.0% and 1.5% of β-glucans showed higher activities compared with the rest of the treatments. On the other hand, the analysis of gene expression did not show significant differences between treatments, although a tendency of increase in the expression of IL-10, TGF, MUC2, and OCC was observed with an addition of 1.5% of the prebiotic, but there was a decrease in the fish fed with 2% of the prebiotic. It is possible to include concentrations of between 0.5% and 1.5% of β-glucans in the diets for A. tropicus, with no detectable adverse effects on growth, survival, digestive enzyme activity, or specific gene expression. β-glucan 1,3/1,6 added at 1.0% and 1.5% in the diet significantly increases chymotrypsin activity.
Highlights
Aquaculture in the southeast of Mexico has great potential, especially with the use of native freshwater species, significant among which is the tropical gar, or so-called pejelagarto (Atractosteus tropicus, Gill 1863)
No significant differences were observed in survival or growth variables, such as final weight, total length, specific growth rate (SGR), feed conversion ratio (FCR) and condition factor (K) values (Table 1)
The diseases generate great economic losses during culture; the use ofconditions immunostimulants hasensuing diseases generate great economic losses[21], during culture; the use being of immunostimulants has increased in the aquaculture industry with the prebiotic β-1,3/1,6-glucan one of the most frequently used
Summary
Aquaculture in the southeast of Mexico has great potential, especially with the use of native freshwater species, significant among which is the tropical gar, or so-called pejelagarto (Atractosteus tropicus, Gill 1863). Health impacts due to outbreaks of diseases under culture conditions generate large economic losses [6]; to reduce this impact, the use of immunostimulants could enhance the immune response and increase resistance of the organism against infectious diseases [7] In this regard, β-glucans are one of the prebiotics with greater interest in the area of aquaculture. The β-1,3/1,6-glucan from the cell walls of yeast (Saccharomyces cerevisiae, Hansen 1883) is one the most studied prebiotics, and is composed of a heterogeneous group of glucose polymers consisting of a backbone of β-1,3-linked β–D–glucopyranosyl units with β-1,6-linked side chains of varying distribution and length Such chemical structures are abundant in microbial communities and can be termed pathogen-associated molecular patterns (PAMP), which play a role as alarm molecules to activate the immune system [8] via their binding to pattern recognition receptors (PRRs), such as
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