Where Do Chickens Get B12: Dietary Sources and Microbial Synthesis

November 24, 2025 •

4 min read

Vitamin B12 is unique because neither plants nor animals can produce it; instead, certain bacteria and archaea are responsible for its synthesis. This means that when asking "where do chickens get B12?" the answer is a combination of dietary intake of animal products or supplements and microbial activity within their digestive tract. For optimal health, modern poultry farming and backyard chicken keeping often require careful management of these sources.

Quick Summary

Chickens, like most animals, cannot produce their own vitamin B12. They obtain it from their diet, primarily through consuming animal-based proteins and, to a lesser extent, from beneficial bacteria within their own digestive systems. Modern poultry feed is often fortified with B12 to ensure proper levels, preventing deficiencies that can impact growth, health, and egg production.

Key Points

Dietary Dependency: Chickens, like humans, cannot synthesize their own vitamin B12 and must get it from their diet.
Sources of B12: Primary sources include animal-based proteins in commercial feed, natural foraging (insects, grubs), and fortified supplements.
Microbial Production: B12 is produced by bacteria in the chicken's cecum, but it is often not effectively absorbed without the practice of coprophagy (ingesting feces).
Supplementation is Standard: Modern farming relies on B12 supplementation in feed to ensure consistent and adequate levels, as wild foraging is no longer a reliable source due to environmental factors.
Deficiency Symptoms: Inadequate B12 can lead to poor growth, anemia, nervous disorders, and reduced egg production and hatchability.
Monitoring and Intervention: Regular monitoring and strategic supplementation, particularly during stress or illness, can prevent deficiency-related health issues.

The Importance of Vitamin B12 for Poultry Health

Vitamin B12, or cobalamin, is a critical water-soluble nutrient for a chicken's overall health and well-being. It acts as a coenzyme in several metabolic processes, including the metabolism of fats, proteins, and carbohydrates. Without adequate B12, chickens can suffer from serious health problems, such as anemia, poor feathering, nervous disorders, and reduced growth rates. For laying hens, B12 is vital for maintaining egg weight and hatchability. Therefore, understanding the sources of this essential vitamin is crucial for responsible chicken care.

Dietary Sources of Vitamin B12

For omnivorous animals like chickens, the primary way to get vitamin B12 is through their diet. In modern commercial and backyard settings, this typically comes from a variety of sources.

Animal-Based Meals: In commercial feeds, animal by-products are a significant source of B12. These can include fish meal, blood meal, feather meal, and whey. Wild chickens and free-range fowl might naturally acquire B12 from insects, grubs, and worms in the soil.
Fortified Feeds: The most common and reliable source for commercially raised chickens is fortified feed, which contains vitamin B12 supplements. This ensures consistent and adequate vitamin levels, which is especially important for flocks raised in controlled environments without access to natural foraging opportunities.
Fermented Foods: Certain fermented foods can contain B12, produced by the bacteria involved in the fermentation process. While not a primary source in commercial settings, some backyard keepers might include fermented grains in their chickens' diets.
Coprophagy: Chickens practice coprophagy, the ingestion of feces, which allows them to benefit from the B12 produced by bacteria in their lower digestive tract, specifically the cecum. This behavior, particularly when birds are kept on deep litter, helps them recycle some of the vitamin produced internally.

The Role of Microbial Synthesis

While chickens cannot produce B12 themselves, the microorganisms living in their digestive tract, primarily in the cecum, are capable of synthesizing it. However, this microbial synthesis often occurs in a part of the intestine that is downstream from the main absorption sites. For this reason, the B12 produced in the gut is not effectively absorbed unless the chicken re-ingests its feces, as described in coprophagy.

The interplay between diet and gut microbes is summarized below:

B12 Synthesis: Certain bacteria in the chicken's cecum produce B12 from cobalt, a mineral they must ingest.
Absorption Challenges: The vitamin produced in the cecum is often passed out of the body in droppings before it can be effectively absorbed.
Access to Microbes: Free-ranging chickens naturally peck at the ground and consume insects, giving them better access to naturally occurring B12 and the microbes that produce it.
Litter and Foraging: Chickens with access to litter or foraging areas are more likely to ingest feces, a natural behavior that helps them utilize the B12 synthesized in their hindgut.

Comparison of B12 Sourcing Methods


Feature	Commercial Fortified Feed	Free-Range Foraging	Microbial Synthesis (Cecum)
Source	Animal by-products, synthetic additives	Insects, grubs, wild plants, soil bacteria	Bacteria in the chicken's cecum
Reliability	Very high; consistent dosing	Variable; depends on environment and diet	Unreliable; depends on coprophagy and absorption
Cost	Part of commercial feed costs	Low to no cost for the chicken keeper	No direct cost
Availability	Readily available	Limited by season, climate, and space	Inherent in the chicken's biology
Absorption	Highly efficient absorption	Good, through consumption of B12-rich sources	Inefficient without coprophagy
Risk of Deficiency	Low, if fed a complete diet	Higher risk if poor foraging or soil	Highest risk if diet is solely plant-based

Ensuring Adequate B12 for Your Flock

Whether you are a commercial producer or a backyard enthusiast, it is important to ensure your chickens have a reliable source of B12. A well-balanced, complete feed is the most straightforward method. For backyard flocks, offering opportunities for foraging can provide some B12, but it should not be the sole source, especially if the chickens are primarily grain-fed. In cases of deficiency symptoms, such as lethargy or poor growth, supplementation via water additives or injections may be necessary. Consulting a poultry veterinarian can help determine the best course of action. For more information on vitamin deficiencies in poultry, the Merck Veterinary Manual provides detailed insights.

Conclusion

In summary, chickens acquire vitamin B12 through a combination of their diet and natural microbial processes. As monogastric animals, they cannot produce sufficient quantities on their own and rely on external sources. The most reliable method is feeding a complete, fortified feed that contains animal-based proteins or synthetic B12. While free-ranging and microbial synthesis offer some benefits, they are generally not sufficient for optimal health and production. Recognizing the signs of a B12 deficiency and providing proper supplementation when needed are key to maintaining a healthy and productive flock.

Frequently Asked Questions

No, chickens cannot get sufficient vitamin B12 from a purely plant-based diet. Like most animals, they require external sources of B12, as plants do not contain it.

While free-range chickens can acquire some B12 by eating insects, grubs, and soil microbes, this is often not enough to meet their nutritional requirements, especially for high-producing layers. Fortified feed is still the most reliable source.

Signs of a B12 deficiency can include reduced weight gain, lethargy, poor feathering, nervous system issues, and a decrease in egg size and hatchability.

Yes, bacteria in a chicken's cecum can synthesize B12. However, due to the location, the vitamin is not efficiently absorbed and is often re-ingested through coprophagy.

Commercial feeds typically use animal-based meals like fish meal, blood meal, feather meal, and sometimes fortified supplements to provide adequate B12.

B12 can be supplemented through fortified feed, water additives, or, in severe cases, injections. Commercially available supplements like 'Rooster Booster' are an option for backyard keepers.

B12 is crucial for laying hens as it affects egg production, egg weight, and hatchability. Adequate intake ensures optimal reproductive performance.