Mannan-oligosaccharides (MOS) are non-digestible carbohydrates, and their use in aquaculture as prebiotics is well documented. The objective of this work was to test whether MOS supplemented in the diet of A. tropicus larvae (2, 4, and 6 g kg−1) influence growth parameters, the activity of digestive enzymes, and the expression of genes related to the intestinal barrier. The highest total length was observed in larvae fed 6 g kg−1 MOS compared to control larvae. Trypsin activity increased with the addition of MOS to the diets, but leucine aminopeptidase activity only increased with 6 g kg−1 MOS. Lipase and α-amylase activities increased in larvae fed with 2 and 4 g kg−1 MOS. The expression of zo-2 was higher with the 6 g kg−1 MOS treatment. The cl-3 transcripts were lower with 2 g kg−1 MOS but higher with 6 g kg−1 MOS. All tested concentrations of MOS increased the expression of muc-2. In this study, incorporating mannan-oligosaccharides into the diet of A. tropicus larvae had a positive effect, and the concentration of 6 g kg−1 produced the best results. Therefore, including this prebiotic in the diets for the culture of A. tropicus larvae is suitable.
The effect of adding inulin to balanced diets for tropical gar (Atractosteus tropicus) larvae on growth, survival, digestive enzyme activity, and antioxidant activity was evaluated. The diets were supplemented with 0.5, 1.0, 1.5, 2.0, and 2.5% inulin in addition to a control diet (0% inulin). A total of 1800 larvae of A. tropicus distributed in 18 tanks were used; the larvae were fed five times a day (8:00, 11:00, 13:00, 15:00, and 18:00) with Artemia nauplii from the absorption of the yolk (from 3–7 days after hatching, DAH) up to 10 DAH, which was mixed with the experimental feeds from 8–11 DAH (co-feeding) and exclusively with the balanced diets from 12 DAH to 21 DAH. Larvae fed the control diet (0% inulin) had the highest growth in weight and length, followed by fish fed the 2.5 and 2.0% inulin inclusions. However, survival showed that the fish fed with the inclusion of 2.5% inulin had the highest percentage (34.7%) compared to the rest of the treatments. On the other hand, the highest digestive enzymatic activities (acid and alkaline proteases, amylase, and lipase) were recorded in the larvae fed with 2 and 2.5% inulin. Likewise, catalase (CAT) and superoxide dismutase (SOD) activities were higher in larvae fed the control diet with 0% inulin. Supplementation of 2.0% to 2.5% inulin in the diet is recommended for A. tropicus larvae as it improves survival and digestive enzyme activity during this early stage of life.
This study was conducted to investigate the effects of dietary fructooligosaccharides (FOS) on the growth, survival rate, digestive enzyms activity, and the expression of intestinal barrier function genes in tropical gar (Atractosteus tropicus) larvae. A total of 960 larvae (0.030 ± 0.006 g) were fed three diets supplemented with increasing FOS concentrations (2.5, 5, and 7.5 g kg−1) and a control diet for 15 days. Results revealed that a 7.5 g kg−1 FOS supplementation improved weight gain, specific growth rate, and survival rate (p < 0.05). Furthermore, 5 g kg−1 FOS supplementation increased alkaline protease and amylase activities and induced an upregulation of the claudin-17 gene expression (p < 0.05). Meanwhile, the inclusion of 7.5 g kg−1 FOS induced the upregulation of mucin 2 (muc-2), and the tight junction genes zo-2 and claudin-3 (p < 0.05). In addition, 2.5, 5, and 7.5 g kg−1 FOS promoted the downregulation of the claudin-15 gene expression (p < 0.05). At the same time, FOS inclusion did not increase the pro-inflammatory cytokine il-8 expression. We can conclude that 7.5 g kg−1 FOS supplementation improves growth performance, survival rate, and digestive capacity, and could contribute to the reinforcement of the intestinal barrier function of Tropical gar larvae.
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