Acidifiers in Poultry, Livestock, and Aquaculture Nutrition: Types, Benefits, and Practical Applications
In the era of antibiotic-free animal production, maintaining gut health and optimal growth performance is critical. Acidifiers, also known as organic acids, have emerged as powerful feed additives that improve digestion, balance gut microbiota, and enhance nutrient absorption while reducing pathogenic bacteria. They are not only a practical alternative to antibiotic growth promoters but also contribute to overall animal health, productivity, and sustainability. Their applications span poultry, livestock, and aquaculture, supporting both feed efficiency and immune function in a natural, scientifically validated manner.
Introduction
The ban on antibiotic growth promoters in the European Union in 2006 (EU Regulation 1831/2003) significantly accelerated the search for safe and effective non-therapeutic feed additives. Among these, organic acids have gained prominence due to their dual role as antimicrobial agents and energy substrates. Chemically, they are weak acids (R-COOH) including formic, acetic, propionic, lactic, fumaric, and citric acids, among others. Their antimicrobial activity depends on pKa, molecular weight, and feed buffering capacity, allowing undissociated forms to penetrate bacterial cell walls, disrupt metabolism, and inhibit pathogens. In addition, acidifiers lower gastrointestinal pH, improve nutrient digestibility, and can be administered via feed, water, or litter. This review explores the types, mechanisms, and practical applications of acidifiers in poultry nutrition, highlighting both feed and environmental uses.
Types of Acidifiers
Based on their physical form and functional characteristics, acidifiers can be classified into three main categories:
Liquid Acidifiers
Liquid acidifiers are highly soluble and are commonly applied through feed or drinking water. They act rapidly by reducing gastrointestinal pH and inhibiting pathogenic microorganisms.
Examples: Formic acid, acetic acid, propionic acid
Typical applications: involve precise dosage control, drinking water sanitation, and rapid antimicrobial action.
Solid or Granular Acidifiers
Solid acidifiers exhibit greater stability during feed processing and allow a more gradual release along the gastrointestinal tract. Common examples are fumaric acid, citric acid, calcium propionate, and calcium lactate.
They are widely used in feed premixes and complete diets.
Examples: Fumaric acid, citric acid, calcium propionate, calcium lactate
Applications: Feed premixes and complete feeds
Buffered Acidifiers and Acid Salts
Buffered acidifiers and acid salts are less corrosive, safer to handle, and often more palatable than free acids.These forms contribute to a more stable gastrointestinal pH over time.
Examples: Calcium formate, sodium formate
| Table 1. Common Organic Acids and Salts Used in Animal Nutrition | |||||
| Organic Acid / Salt | pKa | Solubility | Physical Form | Energy (KJ/g) | Practical Applications |
| Formic acid | 3.37 | Very good | Liquid | 5.8 | Feed, Water |
| Acetic acid | 4.75 | Very good | Liquid | 14.8 | Feed, Water |
| Propionic acid | 4.78 | Very good | Liquid | 20.8 | Feed, Water |
| Lactic acid | 3.08 | Good | Liquid | 15.1 | Feed, Water |
| Fumaric acid | 3.03/4.44 | Low | Solid | 11.5 | Feed Premix |
| Citric acid | 3.14/5.95 | Very good | Solid | 10.3 | Feed, Water |
| Calcium formate | – | Low | Solid | 3.9 | Feed Premix |
| Sodium formate | – | Very good | Solid | 3.9 | Feed Premix |
| Calcium propionate | – | Good | Solid | 16.6 | Feed Premix |
| Calcium lactate | – | Low | Solid | 10.2 | Feed Premix |
Mechanisms of Action
Organic acidifiers exert their beneficial effects through multiple, complementary mechanisms.
- pH Reduction and Antimicrobial Activity
Undissociated organic acids penetrate bacterial cells and dissociate intracellularly, releasing hydrogen ions (H⁺).
This process disrupts enzyme activity, interferes with energy metabolism, and inhibits pathogenic bacteria such as Escherichia coli and Salmonella spp. At the same time, acidifiers favor the proliferation of beneficial microorganisms, including Lactobacillus and Bifidobacterium species.
- Improved Digestibility and Nutrient Absorption
Lower gastrointestinal pH enhances digestive enzyme activity and increases mineral solubility and bioavailability, particularly calcium, magnesium, phosphorus, and zinc.
- Energy Supply for Intestinal Cells
Certain organic acids, such as fumaric, citric, and butyric acids, can enter the Krebs cycle and serve as energy sources for intestinal epithelial cells and beneficial microbiota, thereby supporting gut integrity and function.
- Gut Morphology and Immune Modulation
Studies have reported increased villus height, reduced crypt depth, enhanced intestinal barrier function, and stimulation of local immune responses, contributing to improved disease resistance.
Practical Applications in Poultry, Livestock, and Aquaculture
Poultry
- Broilers: Improved feed conversion ratio, body weight gain, and carcass quality through the use of blends containing formic, fumaric, citric, lactic, and acetic acids.
- Layers: Enhanced egg production, improved eggshell strength, better albumen quality, and increased mineral absorption.
Livestock
- Swine: Reduction of post-weaning diarrhea, stabilization of gut microbiota, and improved growth performance.
- Young ruminants: Stabilization of abomasal pH, improved mineral absorption, and enhanced feed efficiency.
Aquaculture
Acidifiers contribute to improved water pH stability, reduction of pathogenic bacteria, enhanced feed digestibility, better growth performance, and strengthened immune responses in aquatic species.
Environmental and Litter Acidifiers
In addition to dietary applications, acidifiers are also used as environmental or litter treatments. Products such as formic acid–based sprays reduce ammonia emissions and microbial load in bedding materials, thereby improving air quality and animal welfare. These applications are complementary to, rather than replacements for, feed-based acidifiers.
Effects on Performance, Health, Microbiota, and Blood Parameters
- Growth Performance: Improved digestibility of protein, fiber, and energy, leading to better feed conversion and carcass yield.
- Microbiota Modulation: Suppression of pathogenic bacteria and promotion of beneficial microbial populations.
- Blood Biochemistry: Increased serum protein, albumin, calcium, and phosphorus levels, along with reduced LDL cholesterol.
- Immune Function: Strengthening of the intestinal mucosal barrier, increased IgA production, and enhanced antimicrobial peptide activity.
- Economic Benefits: Reduced medication costs, improved feed efficiency, and increased overall productivity.
Tips for correct poultry feed storage and checking its conditions
Conclusion
Feed acidifiers represent multifunctional, evidence-based alternatives to antibiotic growth promoters in modern animal production systems. Their effectiveness depends on factors such as acid type, inclusion rate, diet composition, and method of application. When properly formulated and applied, acidifiers significantly improve gut health, nutrient utilization, microbial balance, immune function, and animal performance. Environmental acidifiers further complement nutritional strategies by improving hygiene and housing conditions, thereby supporting sustainable and economically viable production.
Reference:
Gerzilov, V., & Hristakieva, P. (2025). Organic acids supplementation in poultry nutrition: A review. Open Veterinary Journal, 15(8), 3448.
Khan, S. H., & Iqbal, J. (2016). Recent advances in the role of organic acids in poultry nutrition. Journal of applied animal research, 44(1), 359-369.