Mode of Action of Organic Acids in Poultry: pH & Bacteria Control

To fully leverage the application of organic acids in poultry nutrition, producers must understand exactly how these compounds interact with both the bird's physiology and pathogenic bacteria.

The efficacy of an acidifier is not magic; it is chemistry. The mode of action generally operates through two primary mechanisms: environmental modification and direct intracellular action.

1. Environmental Modification (pH Reduction)

The first mode of action is the reduction of pH in the feed and the upper gastrointestinal tract (crop and proventriculus).

• Enzyme Activation: By lowering the gastric pH, organic acids create the optimal environment for activating pepsin. This improves protein digestion, reducing the amount of undigested substrate available for pathogens in the hindgut.

• Barrier Function: A low pH creates a hostile barrier against acid-intolerant bacteria like E. coli and Salmonella, preventing them from colonizing the gut.

2. Direct Antimicrobial Action (The pKa Factor)

The true power of organic acids lies in their ability to penetrate bacteria. This depends on the acid's pKa value—the pH at which the acid is 50% dissociated and 50% undissociated.

• Penetration: In the acidic environment of the stomach, organic acids remain in their undissociated (neutral) form. This allows them to easily cross the lipid membrane of the bacterial cell wall.

• Dissociation: Once inside the bacterium (where pH is neutral), the acid dissociates, releasing protons (H+) and anions.

• Cell Death: The bacterium is forced to expend all its energy pumping out these protons to maintain its internal balance, eventually leading to exhaustion and cell death. The anion accumulation further disrupts DNA synthesis.

Application in Nutrition

Applying this science requires precision.

• Feed Application: Focuses on hygiene and preventing recontamination of feed stuffs.

• Water Application: Used for critical periods (brooding, feed changes) to rapidly lower gut pH and control waterborne pathogens.

Summary

The role of organic acids in poultry extends beyond simple acidification. They act as targeted antimicrobial agents. By selecting acids with the right pKa and mode of action, producers can effectively replace antibiotics and enhance flock performance.