Utilizing Fermented Banana Peel as a Protein Source to Practically Replace Basa Fish's (Pangasius bocourti) Dietary Protein Content

Technical Summary: Utilizing Fermented Banana Peel as a Protein Source to Replace Soybean Meal in Basa Fish Diets

Problem Statement
The aquaculture industry relies heavily on fish meal and soybean meal (SBM) as primary protein sources. However, fish meal is expensive and derived from wild-caught stocks, while SBM is a costly agricultural commodity. Concurrently, agricultural processing generates significant waste; specifically, Egypt produces 1.21 million tons of bananas annually, resulting in large quantities of banana peels that are often discarded, causing environmental harm. While banana peels contain valuable nutrients (protein, carbohydrates, phytochemicals), their direct use in animal feed is limited by anti-nutritional factors (ANFs) and low protein bioavailability in their raw state. The study addresses the need to find a low-cost, sustainable alternative protein source that can replace SBM in the diets of Pangasius bocourti (Basa fish) without compromising growth or health, utilizing fermentation to mitigate ANFs and enhance nutritional value.

Methodology
The researchers conducted a 12-week feeding trial using 60 Basa fish fingerlings (average initial weight 7.5 g) distributed into 15 tanks (20 fish per tank, three replicates per treatment). Five isonitrogenous diets were formulated to replace SBM with molasses and urea-fermented banana peel (FBP) at inclusion levels of 0% (Control), 25%, 50%, 75%, and 100%.

The FBP preparation involved drying banana peels at 50°C, grinding them, and fermenting a mixture of 1 kg peels, 2.5% molasses, 3% urea, and 1 liter of distilled water for 28 days, followed by drying at 60°C.

Key parameters measured included:

• Growth Performance: Weight gain, specific growth rate (SGR), feed conversion ratio (FCR), and survival rate.
• Digestibility: Apparent digestibility coefficients (ADC) for protein, energy, and dry matter.
• Biochemical Analysis: Blood parameters (hematocrit, hemoglobin, RBCs, WBCs), plasma metabolites (glucose, total protein, lipids, cholesterol), and liver enzymes (AST).
• Enzymatic Activity: Digestive enzyme activities (amylase, lipase, protease) and hepatic glycogen levels.
• Histology: Microscopic examination of liver and intestinal tissues to assess structural integrity.
• Economic Evaluation: Calculation of feed costs per kilogram and cost per kilogram of weight gain.

Key Results

• Nutritional Enhancement: Fermentation significantly increased the crude protein content of banana peels from 9.62% (raw) to 25.01% (fermented), while reducing crude fiber and ash content.
• Growth and Feed Utilization: Fish fed diets with 25% and 50% FBP replacement exhibited superior growth performance, feed conversion ratios (FCR), and survival rates compared to the control and higher replacement groups. The 25% and 50% groups showed the highest apparent digestible energy (ADE).
• Digestibility: Apparent digestibility coefficients for protein, energy, and dry matter remained above 90% for the 25% and 50% groups. The 25% FBP group demonstrated superior energy digestibility compared to other groups.
• Biochemical and Hematological Indices:
  • The 25% and 50% FBP groups showed elevated digestive enzyme activities (amylase, lipase, protease) and increased erythrocyte counts.
  • Plasma total protein, lipid profiles, and AST levels were reduced in these groups.
  • Hematological data indicated decreased hematocrit and hemoglobin but increased red blood cell counts in the 25% and 50% groups.
  • The 25% group specifically showed higher blood glucose and hepatic glycogen levels but lower plasma cholesterol compared to the control and higher inclusion groups.
• Histological Findings: The 25% replacement level resulted in the best tissue structure, showing normal hepatocytes and healthy intestinal villi. In contrast, higher inclusion levels (50%, 75%, and 100%) exhibited tissue deformations, including pyknotic nuclei, vacuoles, dilated vessels, and necrotic tissue in the liver, and abnormal villi in the intestine.
• Economic Impact: While the cost per kilogram of feed decreased as FBP inclusion increased (from LE 33.20/kg for control to LE 28.71/kg for 100% FBP), the feed required to produce 1 kg of fish increased significantly at high replacement levels (2.1 kg for control vs. 2.98 kg for 100% FBP). The 25% and 50% levels offered the most favorable balance between cost reduction and production efficiency.

Significance and Claims
The paper concludes that fermented banana peel (FBP) is a viable and efficient alternative protein source for Basa fish (Pangasius bocourti). The study claims that FBP can successfully replace soybean meal by 25% or 50% without negatively affecting growth, survival, or feed utilization. In fact, these specific replacement levels resulted in the highest overall performance, including growth rates, feed efficiency, and economic viability under the experimental conditions.

The authors assert that the fermentation process effectively degrades anti-nutritional factors and enhances protein quality, making the waste product suitable for aquaculture. The study highlights that while higher replacement levels (75–100%) are economically cheaper per unit of feed, they compromise fish health (evidenced by histological damage and reduced growth efficiency), making the 25–50% range the optimal practical application for sustainable and profitable aquaculture.