Table of Contents
Effects of Algal-Derived β-Glucan on Eel Growth Performance
In a comprehensive 8-week feeding trial, 300 ricefield eels were randomly assigned to five different groups, with one acting as a control (A1, basal diet) and the others receiving diets supplemented with varying concentrations of β-glucan (A2: 250 mg/kg, A3: 500 mg/kg, A4: 1000 mg/kg, A5: 2000 mg/kg). The results demonstrated that the addition of β-glucan significantly enhanced the growth performance of the eels, particularly at concentrations between 0.1% and 0.2%. In particular, the eels in group A4 exhibited the highest weight gain and improvement in feed conversion ratio (FCR), indicating that an optimal dose of β-glucan positively influences growth metrics.
| Group | Initial Body Weight (g) | Final Body Weight (g) | Weight Gain Rate (%) | Specific Growth Rate (%) | Feed Conversion Ratio |
|---|---|---|---|---|---|
| A1 | 12.38 ± 0.50 | 21.68 ± 0.78 | 63.50 ± 5.91 | 0.82 ± 0.06 | 2.63 ± 0.22 |
| A2 | 12.38 ± 0.50 | 29.20 ± 0.68 | 120.21 ± 5.11 | 1.31 ± 0.04 | 1.38 ± 0.06 |
| A3 | 12.38 ± 0.50 | 30.44 ± 1.22 | 130.02 ± 9.54 | 1.39 ± 0.07 | 1.28 ± 0.10 |
| A4 | 12.38 ± 0.50 | 32.80 ± 0.87 | 147.36 ± 6.57 | 1.51 ± 0.04 | 1.12 ± 0.05 |
| A5 | 12.38 ± 0.50 | 30.30 ± 0.75 | 128.51 ± 5.65 | 1.38 ± 0.04 | 1.29 ± 0.06 |
Overall, the study indicates that an appropriate concentration of algal-derived β-glucan can significantly enhance the growth performance of ricefield eels, offering a viable alternative to traditional antibiotic treatments.
Impact of β-Glucan on Intestinal Health in Monopterus albus
The intestinal health of eels is crucial for nutrient absorption and overall well-being. The addition of β-glucan has been shown to positively influence intestinal morphology and digestive enzyme activity, which are vital for maintaining health in aquaculture. Histological examinations of intestinal tissues revealed that eels in the β-glucan groups exhibited longer villi and improved intestinal structure compared to the control group.
| Group | Villi Length (µm) |
|---|---|
| A1 | 100 ± 10 |
| A2 | 120 ± 15 |
| A3 | 130 ± 12 |
| A4 | 150 ± 20 |
| A5 | 140 ± 18 |
Additionally, β-glucan supplementation significantly enhanced the activities of key digestive enzymes, including trypsin, amylase, and lipase. These enzymes are essential for the digestion and absorption of nutrients, indicating that β-glucan not only supports growth but also enhances the digestive capacity of eels.
β-Glucan’s Role in Enhancing Aeromonas veronii Resistance
Aeromonas veronii is a pathogenic bacterium commonly associated with high mortality rates in fish. In the study, after challenging the eels with A. veronii, it was observed that β-glucan significantly improved the survival rates among infected eels. The survival rates after 72 hours of infection were as follows:
| Group | Survival Rate (%) |
|---|---|
| A1 | 10 ± 2 |
| A2 | 40 ± 3 |
| A3 | 40 ± 4 |
| A4 | 60 ± 5 |
| A5 | 70 ± 6 |
Moreover, the bacterial load in the liver, spleen, and kidney was significantly reduced in the β-glucan groups compared to the control group, suggesting that β-glucan enhances the immune response and reduces the severity of infections.
Influence of β-Glucan on Digestive Enzymes and Antioxidant Activity
The incorporation of β-glucan into the diet not only improved growth performance and intestinal health but also enhanced the antioxidant capacity of the eels. The activities of superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) were evaluated and demonstrated significant improvements in antioxidant levels in response to β-glucan supplementation.
| Antioxidant Parameter | A1 (Control) | A4 (Optimal β-Glucan) |
|---|---|---|
| SOD (U/mg) | 2.5 ± 0.3 | 4.0 ± 0.5 |
| CAT (U/mg) | 1.2 ± 0.2 | 2.1 ± 0.3 |
| MDA (nmol/g) | 5.5 ± 0.4 | 3.0 ± 0.5 |
These findings suggest that β-glucan acts as an effective antioxidant agent, contributing to the overall health and resilience of ricefield eels.
Changes in Intestinal Microbiota Composition with β-Glucan
The composition of the intestinal microbiota plays a vital role in the health and immunity of aquatic species. In this study, significant changes in the intestinal microbiota were observed with the addition of β-glucan. The relative abundance of Proteobacteria increased while that of Firmicutes decreased, indicating a shift towards a more beneficial microbial community.
| Phylum | A1 (Control) | A4 (Optimal β-Glucan) |
|---|---|---|
| Firmicutes | 60% | 45% |
| Proteobacteria | 30% | 40% |
| Bacteroidota | 5% | 10% |
| Others | 5% | 5% |
The alterations in microbiota composition may contribute to the improved health and disease resistance observed in eels supplemented with β-glucan.
Conclusion
The addition of algal-derived β-glucan in the diets of ricefield eels has been shown to enhance growth performance, improve intestinal health, and increase resistance to pathogens such as Aeromonas veronii. The results indicate that an optimal inclusion rate of 0.1% to 0.2% β-glucan not only benefits the growth metrics of eels but also supports their immune functions and overall health.
Frequently Asked Questions (FAQ)
What is β-glucan and where is it sourced from?
β-glucan is a polysaccharide that is primarily derived from algae and certain cereals. It is known for its immune-boosting properties.
How does β-glucan affect the growth of ricefield eels?
Supplementing β-glucan in the diet significantly improves the growth performance and feed conversion ratio in ricefield eels.
Can β-glucan help in disease resistance?
Yes, studies have shown that β-glucan enhances the immune response and increases the survival rates of eels infected with pathogens like Aeromonas veronii.
Are there any side effects of β-glucan supplementation?
While β-glucan is generally considered safe, excessive amounts may inhibit the absorption of other nutrients, potentially affecting growth negatively.
What changes occur in the intestinal microbiota with β-glucan supplementation?
The addition of β-glucan has been observed to alter the composition of the intestinal microbiota, increasing beneficial bacteria such as Proteobacteria while decreasing Firmicutes.
References
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