INTRODUCTION
Whiteleg shrimp (Litopenaeus vannamei) is one of the most important aquaculture species worldwide, especially in Vietnam. However, diseases remain a major threat to shrimp farming, directly affecting productivity and profitability. In the context of restricted antibiotic use due to concerns over antimicrobial resistance and food safety, organic acids have emerged as a natural and effective solution for the prevention and treatment of diseases in whiteleg shrimp.
1. Overview of Organic Acids
Organic acids are organic compounds that contain one or more carboxyl groups. They include straight-chain, saturated monocarboxylic acids (C1 – C18) and their corresponding derivatives, with the general molecular structure R-COOH, where R represents a monovalent functional group. These acids are commonly referred to as short-chain fatty acids, volatile fatty acids, or weak carboxylic acids.
Organic acids are produced through the fermentation of carbohydrates by various bacterial species under different metabolic processes and conditions.
2. Mechanisms of Action of Organic Acids in the Prevention and Treatment of Diseases in Whiteleg Shrimp
2.1. Lowering Intestinal pH
When introduced into the intestine, organic acids reduce the pH level, creating a mildly acidic environment that stimulates the activity of digestive enzymes, particularly pepsin, which breaks down proteins.
The lower pH environment also inhibits the growth of pathogenic bacteria such as Vibrio parahaemolyticus (the causative agent of Early Mortality Syndrome/Acute Hepatopancreatic Necrosis Disease – EMS/AHPND) and Aeromonas.
2.2. Disruption of Harmful Bacterial Cell Membranes
Organic acids in their non-dissociated form (R-COOH) can penetrate the cell membranes of pathogenic bacteria. Once inside the bacterial cell, they dissociate into hydrogen ions (H⁺) and acid anions (-COO⁻). The hydrogen ions lower the intracellular pH, disrupting homeostasis and inhibiting essential enzymatic activities. The acid anions (-COO⁻) interfere with metabolic processes, ultimately impairing bacterial growth.
Organic acid molecules infiltrate the bacterial cell wall—particularly in Gram-negative bacteria such as Vibrio—and dissociate within the cytoplasm, disturbing cellular functions. Therefore, when used at appropriate doses, mixtures of these acid salts provide a safe, effective, and cost-efficient solution for controlling intestinal bacterial diseases caused by Gram-negative bacteria, while also promoting the development of the host’s gut microbiota.
Mechanism of Action of Organic Acids in Eliminating Harmful Bacteria
2.3. Supporting Digestion and Nutrient Absorption
Organic acids can form complexes with minerals such as calcium (Ca), magnesium (Mg), zinc (Zn), and iron (Fe), making them more easily absorbed through the intestinal lining.
2.4. Inhibiting the Growth of Pathogenic Bacteria
Pathogenic bacteria in the intestines of shrimp and fish often thrive in neutral or alkaline environments. When organic acids lower the pH, these bacteria are weakened and lose their ability to adhere to the intestinal mucosa.
2.5. Stimulating Beneficial Microorganisms
Organic acids help create a favorable environment for the growth of beneficial bacteria such as Lactobacillus and Bacillus. These probiotics help balance the intestinal microbiota, compete with pathogens for adhesion sites, and support the digestion of feed.
3. Common Organic Acids Used in Aquaculture
3.1. Formic Acid (HCOOH)
Broad-spectrum antibacterial activity: Formic acid is highly effective against many important pathogenic bacteria in shrimp farming, such as Vibrio parahaemolyticus (which causes Acute Hepatopancreatic Necrosis Disease – AHPND and Translucent Postlarvae Disease – TPD), Vibrio harveyi (which causes luminous vibriosis), Aeromonas (which causes hemorrhagic disease), and Edwardsiella (which causes intestinal disease).
Enhanced efficacy through combination: When combined with other acids (such as propionic acid, lactic acid, and citric acid), its antibacterial effect is further enhanced due to synergistic interactions.
Strongly recommended for use: The use of formic acid is highly encouraged. Several studies have shown that supplementing shrimp diets with formic acid helps suppress pathogens, reduce mortality rates, and support more environmentally friendly shrimp production.
Multacid Product Containing Formic Acid
3.2. Propionic Acid (C₂H₅COOH)
– A short-chain organic acid, commonly used in combination with formic acid or lactic acid.
– Inhibits the growth of harmful molds and bacteria such as Aspergillus, Penicillium, and Fusarium (which spoil feed), thereby improving feed preservation and reducing microbial contamination.
– Helps control Vibrio spp. (causing Acute Hepatopancreatic Necrosis Disease – AHPND) and reduces Aeromonas spp. (which cause hemorrhagic and intestinal diseases).
– Creates a favorable environment for beneficial bacteria (probiotics), promoting the growth of Lactobacillus and Bacillus.
– Enhances the absorption of minerals (Ca, P, Mg), helping shrimp harden their shells faster after molting.
– Stimulates digestive enzymes, improving the absorption of proteins, lipids, and energy in shrimp.
3.3. Butyric Acid (C₄H₈O₂)
– Produced through the fermentation of fiber by gut bacteria or industrially in the form of butyrate salts.
– Supports the growth of beneficial bacteria (Lactobacillus, Bacillus) and inhibits harmful bacteria.
– Helps shrimp combat intestinal diseases, particularly white feces syndrome; aids digestion, protects the hepatopancreas, and enhances immunity.
Comparison Table of the Functions of Some Organic Acids in Aquaculture
4. Application of Organic Acids in Disease Prevention for Shrimp Farming
– Formic Acid: Widely used to inhibit pathogenic bacteria in the gut.
**Recommended dosage: 2-3 ml/kg of feed, depending on the type of acid and the intended purpose.
– Butyric Acid: Improves gut health and inhibits harmful bacteria.
**Recommended dosage: Mix 2-3 ml/kg of feed.
– Propionic Acid: Helps control pH and reduce the density of pathogenic bacteria in the water environment.
**Usage method: Dissolve the organic acid in water and apply to the pond at the appropriate dosage (0.5-1 liter per 1,000 m³ of water, depending on the type of acid).
5. Application of Organic Acids in Disease Treatment for Shrimp Farming
In cases where shrimp are already infected, organic acids can be used in combination with other methods to support the recovery process:
- Treatment of Acute Hepatopancreatic Necrosis Disease (AHPND): Use formic acid or a mixture of organic acids in the feed to reduce Vibrio bacteria in the shrimp’s gut.
- Treatment of White Feces Disease: Organic acids help balance the gut microbiota and inhibit the growth of Enterocytozoon hepatopenaei (EHP).
- Boosting Immunity After Disease Treatment: Supplementing with citric acid and lactic acid helps improve nutrient absorption and supports shrimp health recovery.
Customers interested in organic acid products, please contact Truong Hai Tien. We offer high-quality organic acid products in various formulations and reasonable prices, ensuring you select the best product for your needs!
