Phytogenics in Poultry: Can Plants Help Support Bird Health?

As the poultry industry moves towards more responsible antimicrobial use, there has been growing interest in alternatives that may help support gut health, performance and resilience.

One group attracting considerable research attention is phytogenics.

Also known as phytogenic feed additives or botanicals, phytogenics are plant-derived compounds incorporated into animal diets. They include herbs, spices, essential oils and plant extracts.

Oregano and thyme are probably two of the best-known examples, but the category is much broader.

What Are Phytogenic Feed Additives?

Phytogenics can be broadly grouped into:

• Herbs, such as oregano, rosemary and thyme
• Spices, including compounds derived from plants such as ginger and cinnamon
• Essential oils, concentrated aromatic compounds extracted from plant material
• Oleoresins and extracts, concentrated mixtures obtained from herbs and spices

Much of the interest in these products comes from the biologically active compounds they contain.

For example, oregano is particularly associated with carvacrol, while thyme is an important source of thymol.

How Might Phytogenics Work?

One of the interesting things about phytogenics is that they don't necessarily have a single mechanism of action.

Depending on the plant, concentration, formulation and combination of compounds, research suggests they may influence several biological processes.

Supporting Gut Function

Some phytogenic compounds may influence digestive secretions, intestinal motility and digestive enzyme activity.

They may also interact with the intestinal microbiome and gut barrier.

This has generated particular interest in poultry production, where maintaining good intestinal function is closely linked with health, feed utilisation and performance.

Antioxidant Activity

Plants such as oregano, thyme and rosemary contain compounds with antioxidant properties.

These compounds can help reduce oxidative damage caused by reactive oxygen species and may contribute to the animal's overall antioxidant defence system.

Importantly, antioxidant effects demonstrated in laboratory studies don't always translate directly into the same effect in a living bird. Dose, formulation and bioavailability matter.

Antimicrobial Activity

This is probably the most widely discussed property of phytogenics.

Compounds including carvacrol and thymol have demonstrated antimicrobial activity against a range of microorganisms under laboratory conditions.

Studies have investigated activity against bacteria including Escherichia coli, Staphylococcus aureus and Listeria species.

However, there is an important distinction between in vitro antimicrobial activity and treating an infection in a bird.

A substance killing bacteria in a laboratory does not automatically make it an effective antibiotic replacement for a clinically sick animal.

Anti-inflammatory Effects

A number of phytogenic compounds have also been investigated for their effects on inflammatory pathways.

Rather than thinking of these compounds as conventional anti-inflammatory medications, it is more accurate to consider them biologically active substances that may influence inflammatory responses.

This remains an active area of research.

Antifungal Activity

Some plant-derived compounds also demonstrate antifungal activity.

Carvacrol and thymol, for example, have been investigated against fungal organisms including Candida and Aspergillus species.

Again, laboratory activity should not be confused with evidence that feeding oregano or essential oils will treat fungal disease in a bird.

Oregano and Carvacrol

Oregano has become one of the most widely recognised phytogenic ingredients in poultry nutrition.

Much of the research interest surrounds carvacrol, one of the principal bioactive compounds found in oregano essential oil.

Carvacrol has been investigated for its:

• Antimicrobial activity
• Antioxidant properties
• Effects on intestinal health
• Influence on inflammatory pathways
• Potential effects on feed utilisation and performance

This doesn't mean that simply adding oregano from the kitchen to chicken feed will reproduce the results seen in controlled studies.

Commercial phytogenic products may use standardised extracts, specific concentrations or combinations of active compounds. That makes comparison with whole herbs or homemade essential oil preparations difficult.

Can Phytogenics Replace Antibiotics?

This is where we need to be careful.

Phytogenics are sometimes marketed as natural alternatives to antibiotics, but that description can be misleading.

They may form part of a management system designed to improve intestinal health and reduce disease pressure, potentially reducing the circumstances in which antimicrobial treatment becomes necessary.

That is very different from saying they can replace antibiotics when a bird has a bacterial infection requiring treatment.

The bigger opportunity is preventative management.

Good nutrition, biosecurity, vaccination where appropriate, hygiene, appropriate stocking density, parasite management and gut-supporting strategies can all reduce disease pressure. Phytogenics may be another tool within that system.

Natural Doesn't Automatically Mean Safe

One of the most important things to remember about phytogenics is that natural does not mean harmless.

Plants produce biologically active chemicals precisely because those chemicals have effects on other organisms.

Essential oils in particular can be extremely concentrated.

The safety of a phytogenic product depends on factors including:

• The plant species
• Active compounds
• Concentration
• Dose
• Method of administration
• Duration of exposure
• Bird species and age
• Interactions between different compounds

A carefully formulated feed additive is very different from adding concentrated essential oils directly to drinking water or feed without knowing the final dose.

Phytogenics Are Part of a Bigger Picture

Phytogenics are interesting because they represent a move away from thinking about animal health purely in terms of treating disease after it appears.

Instead, we can ask how nutrition, the microbiome, environment, biosecurity and management can work together to make animals more resilient in the first place.

They aren't miracle products, and they aren't replacements for veterinary medicine.

But as part of a broader preventative health strategy, phytogenics represent a fascinating and rapidly developing area of poultry nutrition and animal health.

The Takeaway

Plant-derived compounds such as carvacrol and thymol have demonstrated antimicrobial, antioxidant and other biological activities, and there is growing research into their use in poultry nutrition.

The key is not to confuse biological activity with proven clinical treatment.

Used appropriately, phytogenics may become another useful tool alongside good nutrition, biosecurity, husbandry and responsible antimicrobial stewardship.

And that is ultimately where their greatest potential may lie.

Written by Dr Sam Hurley, BSc, BVSc, MAHM