Oxidation in Poultry Feed: Meaning, Classification, and Antioxidant Solutions

1️ Oxidation Meaning and Classification

Definition: Oxidation in feed or within the body involves the loss of electrons by a molecule, atom, or ion. This process is often accelerated by the presence of free radicals or reactive oxygen species (ROS), which are highly reactive molecules formed during normal metabolic activities.

Types of Oxidation:

In-Feed Oxidation: Occurs in stored feed ingredients and premixes where fats, vitamins, and proteins undergo oxidation, leading to:

Rancidity in fats and oils, reducing palatability and causing feed refusal.

Nutrient degradation, especially of fat-soluble vitamins like Vitamin E, pigments, and amino acids, which decreases the feed’s nutritive value.

In-Vivo Oxidative Stress: Within the bird, ROS generated through metabolic processes or environmental stressors can overwhelm the bird’s natural antioxidant defenses. When ROS levels exceed the body’s antioxidant capacity, oxidative stress occurs, potentially causing:

Damage to cellular membranes, proteins, DNA, and lipids.

Health issues such as leaky gut, muscle myopathies, and reduced performance.

2️ Nutrients and Agents That Cause Oxidation in Feed

Lipids: Among the most oxidation-sensitive components in poultry diets.

Unsaturated fatty acids, found in vegetable oils like soybean, corn, and sunflower oil, are particularly prone to autoxidation.

Sources of oxidation: Exposure to light, air, and metals (e.g., copper, iron) accelerates lipid oxidation, leading to rancidity and a decrease in energy value.

Vitamins: Fat-soluble vitamins, especially Vitamin E and Vitamin A, can oxidize easily. Once oxidized, these vitamins lose their biological activity, reducing the feed’s antioxidant capacity.
Amino Acids and Pigments: Methionine, lysine, and carotenoids are susceptible to oxidation. This can lower protein quality, affecting growth rates and pigmentation in poultry.
Pro-Oxidant Agents:Transition Metals (e.g., copper, iron): Metals in feed act as catalysts, accelerating the oxidation process.

Environmental Conditions: High temperatures, oxygen exposure, and light exposure can increase oxidation rates in feed ingredients, especially during storage.

3️ Oxidative Stress Agents Affecting Gut Health

Physical Stressors:

Heat Stress: Increases metabolic rate and ROS production, leading to intestinal damage, reduced barrier function, and increased gut permeability, often referred to as “leaky gut.”

High Stocking Density: Crowded conditions increase stress and ROS production, impairing gut health and leading to a higher risk of infections.

Pathological Stressors:

Pathogens (e.g., Eimeria spp. causing coccidiosis): Infection induces ROS production as part of the immune response, damaging the gut epithelium and leading to inflammatory responses.

Mycotoxins (e.g., aflatoxins, deoxynivalenol): These contaminants in feed are major sources of oxidative stress. They generate ROS, leading to cell damage, DNA mutations, and increased gut permeability.

Excess Dietary Metals (e.g., iron): High metal concentrations increase ROS levels, altering gut microbiota and intestinal health, and potentially causing inflammatory conditions.

4️ Key Antioxidant Nutrients and Recommended Dosages

Natural Antioxidants:

Vitamin E: Fat-soluble and essential for cellular defense against ROS, especially in protecting lipids from oxidation.

Dosage: Typically added at 100-150 IU/kg feed for general use; in stressful conditions, higher doses up to 300 IU/kg may be used.

Vitamin C: Water-soluble and known for scavenging free radicals; often used to help mitigate the effects of environmental stress.

Dosage: 200-500 mg/kg feed; increased up to 500 mg/kg during periods of heat stress or transportation.

Polyphenols: Natural antioxidants from plant sources (e.g., rosemary, green tea) protect lipids from oxidation.

Rosemary Extract: Commonly used as a natural antioxidant due to its phenolic compounds (e.g., carnosic acid, rosmarinic acid).

Dosage: 200-500 mg/kg feed, depending on the concentration of active compounds.

Synthetic Antioxidants:

Butylated Hydroxytoluene (BHT): A synthetic antioxidant effective at preventing lipid oxidation in feed.

Dosage: Max inclusion of 150 mg/kg feed.

Butylated Hydroxyanisole (BHA): Similar to BHT, prevents peroxyl radical formation, especially in high-temperature processing.

Dosage: Typically 100-150 mg/kg feed.

Propyl Gallate (PG): Scavenges free radicals and is often used in combination with BHT or BHA for synergistic effects.

Dosage: Max inclusion 100 mg/kg feed.

5️ Endogenous and Exogenous Antioxidants in Poultry

Endogenous Antioxidants: Naturally occurring antioxidant enzymes in the bird’s body, including:

Superoxide Dismutase (SOD): Converts superoxide radicals to hydrogen peroxide.

Catalase: Breaks down hydrogen peroxide into water and oxygen.

Glutathione Peroxidase (GPx): Breaks down peroxides, protecting cellular membranes.

Support with Selenium: Supplementing 0.2-0.3 mg/kg feed helps maintain GPx activity.

Exogenous Antioxidants: These are supplemented in feed and support the body’s defenses:

Vitamin E and Vitamin C: As discussed above, these vitamins provide antioxidant support.

Polyphenols: Plant-based antioxidants such as rosemary extract are used to reduce lipid oxidation in feed.

Additional minerals: Zinc (40-80 ppm) supports SOD function, Manganese (30-60 ppm) for catalase activity, and Copper (8-10 ppm) to optimize antioxidant enzyme functions.

6️ Effects of Antioxidants on Performance and Gut Health

Performance Benefits:

Antioxidants help prevent oxidative damage, maintaining gut integrity and nutrient absorption, leading to improved growth rates, feed efficiency, and overall health.

Supplementing Vitamin E, C, and polyphenols has been shown to increase body weight gain (BWG), reduce feed conversion ratio (FCR), and enhance resistance to environmental and physiological stressors.