Organic Acids in Animal Nutrition

Efficiently producing meat and eggs today requires total value extraction from production inputs such as feed. Taking advantage of high performing genetics requires precise nutrition at time when feed ingredient prices are at their highest. Organic acids in animal nutrition support the production and utilization of valuable feed and at the same time uphold comprehensive biosecurity programs.

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Feed-source pathogens such as Salmonella, Clostridia, Campylobacter and E. coli cost producers through diminished feed value, manufacturing and animal productivity constraints, food safety challenges and biosecurity concerns. Organic acids in animal nutrition have historically been used as feed preservatives protecting against feed spoilage. Today, a growing body of literature shows organic acids as feed additives support mitigation of feed-source pathogens and prevent pathogen colonization within swine and poultry gastrointestinal tracts.

 Not every organic acid works for every pathogenic challenge. Specially formulated synergistic organic acid blends possess a broader spectrum of control by capitalizing on the strengths of multiple acids to reduce feed-source pathogen transmission and lower the microbial load of feed. To better understand how synergistic organic acids blends give you more control over feed hygiene, let’s review the basics of organic acids in animal nutrition.

What are Organic Acids?

Organic acids are carbon-containing compounds made up of short and medium-chain fatty acids that possess a pH of less than 7, react with bases to form salts and produce hydrogen ions when dissolved in water. The acidic properties and chemical structure of organic acids are essential to antimicrobial and antifungal function and efficacy.

Organic acids commonly used in animal nutrition fall under the fatty acid classification and include:

• Formic acid
• Propionic acid
• Acetic acid
• Sorbic acid
• Citric acid
• Lactic acid
• Benzoic acid
• Butyric Acid

Every organic acid has specific characteristics that impact its ability to mitigate feed-source enteric pathogens. However, selecting the right organic acid requires producers to consider the pathogen challenge with respect to pathogen type, load and reservoir. The efficacy of organic acids in animal nutrition is dose-dependent but is also impacted by environmental temperature and feed matrix water activity.

Organic Acids as Feed Additives

Often used at higher, optimized doses organic acids support animal production through increased feed conversion and body weight. Organic acids restrict microbial growth and improve metabolic functions by altering the pH in feed and throughout the gastrointestinal tract. However, organic acid efficacy requires delivery of the correct organic acid to the targeted microbial challenge.

For example, one study noted that formic acid has been found to offer effective control against pathogens such as Salmonella and Campylobacter and has a positive impact on broiler growth, protein digestibility and immune function.

Organic Acid Pathogen Specificity

Similar to how organic acids in animal nutrition have specific chemical characteristics, feed-source pathogens also have various survival mechanisms and stress tolerance levels. For instance, Salmonella often exists in feed within a desiccated and stressed state, whereas Clostridia perfringens can produce spores that facilitate survival under suboptimal conditions and as such has a large thermal range in which it can survive. Studies have found that these different types of bacteria have different sensitivities to certain organic acids. Using a single organic acid, even at a high dose, can limit the producer's ability to mitigate pathogens challenging food safety and performance due to their specific properties, however, organic acid blends provide a broader spectrum of control.

This was best demonstrated in a study exploring the antimicrobial activity of organic acids against enteric pathogens linked to swine. Researchers observed that inhibition of E. coli and Salmonella strains required a lower concentration of formic acid than Clostridia perfringens, whereas pelargonic acid (nonanoic acid) had a higher inhibitory effect against Clostridia perfringens than it did Salmonella and E. coli.

Organic Acid Mode of Action

Increased acidity is the primary mechanism driving bacteriostatic action of organic acids and as a result choosing the right organic acid solution requires an understanding of pka values. Organic acids exist in two forms, dissociated and undissociated and their specific pKa value is the measure of how readily and completely the acid dissociates in an aqueous solution. The undissociated form of an organic acid is lipophilic and retains all of its protons (H+), allowing the organic acid to cross cellular membranes.

 Once inside the cell, the organic acid is surrounded by a relatively neutral pH, which causes it to surrender its available protons and increase intracellular acidity, lowering the cellular pH. This action disrupts normal cell function and prevents cell proliferation leading to apoptosis.