Phytogenic Feed Additives for Coccidiosis Control in Poultry

The poultry industry is constantly searching for strategies to protect flock health while ensuring sustainable production. Among the main intestinal diseases affecting poultry, coccidiosis stands out as one of the most damaging and costly worldwide. The use of phytogenic feed additives is an important tool that brings natural bioactivity and a solid scientific base that supports their role in coccidiosis management.

Coccidiosis is a parasitic disease caused by Eimeria protozoa that invade the bird’s intestinal epithelial cells. Each species targets different intestinal segments, from the small intestine to the ceca. Once inside host cells, the parasites multiply and cause tissue destruction, leading to bleeding, diarrhea, and nutrient malabsorption (El-Shall et al., 2022).

Even when mortality is low, subclinical infections impose substantial costs by reducing weight gain, impairing feed conversion, causing uneven flock growth, and predisposing birds to secondary diseases such as necrotic enteritis (El-Shall et al., 2022). The associated global economic losses are estimated to reach several billion dollars annually (Blake et al., 2020).

For decades, ionophores and chemical coccidiostats have been used to manage the disease. However, the emergence of drug resistance, coupled with consumer pressure and residue concerns, has driven interest toward natural, in-feed alternatives (Bozkurt et al., 2016).

In-feed phytogenic solutions are plant-derived compounds incorporated into poultry diets to enhance performance and health. They include:

• Herbs and spices – dried plant materials such as oregano or thyme.
• Essential oils – volatile compounds extracted via steam distillation.
• Plant extracts and saponin-rich fractions – such as those obtained from Yucca or Quillaja.

These additives supply bioactive molecules such as phenolics, terpenes, flavonoids, and saponins that act as antimicrobials, antioxidants, and immune modulators (Gholami-Ahangaran et al., 2022). Rather than relying on a single mechanism, phytogenics create a “multi-hit” defense that makes it more difficult for Eimeria to adapt or develop resistance (Saeed & Alkheraije, 2023).

Recent research indicates that phytogenic compounds can directly disrupt Eimeria lifecycle stages while simultaneously supporting the host’s immune system and antioxidant capacity (Oelschlager et al., 2019; Saeed & Alkheraije, 2023).

Saponins are plant-derived secondary metabolites that foam in water due to their amphipathic structure, consisting of a hydrophobic aglycone linked to sugar chains (Vincken et al., 2007). Saponins are commonly derived from Yucca schidigera and Quillaja saponaria. Yucca schidigera is a desert plant native to North America and is widely used in animal nutrition because of its high content of steroidal saponins, glycosidic compounds with diverse bioactivities (Cheeke, 2000). Quillaja saponaria, also known as (soapbark tree), on the other hand, produces triterpenoid (non-steroidal) saponins (Fenwick et al., 1991).

 Saponins bind sterols such as cholesterol found in cell membranes, making Eimeria particularly susceptible because sporozoites and other life stages contain membrane sterols. When present in the gut via Yucca-supplemented feed, saponins interact with parasite membrane sterols, disrupt membrane integrity, and induce cell lysis (Muthamilselvan et al., 2016).

Their anticoccidial effects include:

• Membrane disruption – formation of pores and loss of integrity in parasite cells (Cheeke, 2000; Muthamilselvan et al., 2016).
• Inhibited invasion and replication – neutralization of sporozoites before cell invasion, impairing parasite development (Muthamilselvan et al., 2016).
• Reduced oocyst shedding – fewer oocysts are released, thus lowering reinfection pressure (Oelschlager et al., 2019).

Experimental and field studies confirm these benefits: broilers fed Yucca extracts during a coccidiosis challenge have shown lower lesion scores and reduced oocyst counts (Kozłowski et al., 2022), improved weight gain (Oelschlager et al., 2019), and even enhanced intestinal villi regeneration (Oelschlager et al., 2019). Moreover, Yucca supplementation has been linked to immune modulation, with changes in gut immune cell populations and cytokine expression that suggest improved resilience to infection (Oelschlager et al., 2019).

Herbs and Essential Oils: Multi-Purpose Defenses

Herbs typically refer to dried plant materials (leaf, stem, or flower parts from plants known for medicinal or aromatic properties), while essential oils (EOs) are their concentrated, volatile extracts (de Sousa et al., 2023). 

Essential oils contain the aromatic compounds that give herbs their characteristic scent and flavor, and often these include powerful bioactive molecules like phenols, terpenes, and aldehydes. Many herbs and their essential oils have natural antimicrobial effects, meaning they can kill or inhibit bacteria, fungi, or even parasites, helping to reduce oxidative stress and promote a healthier gut microbiota, which indirectly limits the parasite’s success (Gordillo Jaramillo et al., 2021).

Oregano Essential Oil: Rich in Carvacrol and Thymol

Oregano essential oil is rich in carvacrol and thymol, phenolic compounds with strong antimicrobial effects, particularly against Gram-positive bacteria such as Clostridium perfringens, the causative agent of necrotic enteritis (Gholami-Ahangaran et al., 2022). Since coccidiosis often predisposes birds to necrotic enteritis, this dual action is highly relevant.

Studies show that oregano oil reduces C. perfringens loads (Mitsch et al., 2004), disrupts bacterial membranes (Burt, 2004), lowers toxin production, and decreases intestinal damage (Bozkurt et al., 2016). In coccidial challenges, oregano essential oil can help to  improve antioxidant status, gut morphology, lesion scores, and performance (Bozkurt et al., 2016)

Thus, oregano essential oil not only combats Eimeria, but also lowers the risk of secondary infections, reinforcing its value in integrated anticoccidial strategies.

Citrus Oil: Limonene and Antioxidant Defense

Citrus essential oils are characterized by their high limonene content. Limonene and related citrus terpenes (like linalool) are known for their antioxidant and mild antimicrobial properties. In poultry, citrus oil is often included in phytogenic blends for its ability to improve feed palatability and to provide antioxidant support to the birds. 

During a coccidia infection, a bird’s intestines undergo oxidative stress and lipid peroxidation due to the intense inflammatory response (El-Shall et al., 2022). Antioxidant compounds like limonene can help counteract this by neutralizing free radicals and by upregulating the bird’s own antioxidant enzymes. Supplemented birds show lower oxidative damage, milder lesions, and improved performance under Eimeria challenge (Bozkurt et al., 2016; Imran & Alsayeqh, 2022). 

Beyond these effects, limonene and related terpenes can directly damage Eimeria oocysts by penetrating the oocyst wall or disrupting parasite membranes (El-Shall et al., 2022). Citrus oil supplementation has also been linked to a healthier gut microbiota during infection (Ouwehand et al., 2010).

Conclusion

Phytogenic feed additives offer a natural, science-based strategy to control coccidiosis while supporting flock performance. They reduce reliance on chemical coccidiostats and ionophores, addressing concerns over resistance and residues. Unlike conventional drugs, they require no withdrawal period, allowing continuous use without marketing restrictions. Their integration into feed programs also supports cost-effective rotation and shuttle strategies, enabling more flexible health management systems. By enhancing bird health and performance under coccidial challenge, phytogenic additives improve profitability and contribute to the long-term sustainability of poultry production.