DOSAGE FORM

The dosage form of a probiotic is a crucial factor in determining the stability, viability, and biological effectiveness of the microorganism when consumed by poultry [224]. Probiotics are available in various forms, such as liquid solutions, capsules, or freeze-dried, each with its own advantages regarding storage, resistance to digestive tract conditions, and ease of application in feed [225].

In commercial practice, the choice of dosage form should also consider economic efficiency, storage logistics, compatibility with feed mill infrastructure, and potential losses during pelleting [12]. Heat-stable spore-forming strains (e.g., Bacillus spp.) may reduce viability losses during feed processing, thereby improving cost-effectiveness compared to heat-sensitive strains requiring protective technologies [226].

In commercial poultry production, probiotic inclusion levels commonly range from 10⁶ to 10⁹ CFU/g of feed, which is equivalent to approximately 10⁷–10⁹ CFU/bird/day depending on feed intake and bird age [227]. Lower inclusion rates (10⁶ CFU/g) are typically used for maintenance of gut microbial balance, whereas higher levels (10⁸–10⁹ CFU/g) are often applied during early-life stages, periods of stress, vaccination, or pathogen challenge. However, optimal dosage remains strain-specific and should be validated under field conditions [222].

Liquid probiotics are generally suspensions of live bacteria in a culture medium, allowing them to be added directly to feed or drinking water. This format simplifies distribution and dosage adjustments, but has limitations related to shelf life and susceptibility to high temperatures and oxygen exposure [208].

Probiotics in capsule form provide physical protection against the acidic environment of the stomach while simplifying dosage adjustments. These capsules typically contain live bacterial cells coated in a protective matrix, increasing the likelihood that the bacteria will remain viable once they reach the intestines [228]. The capsule format also simplifies implementation in long-term supplementation programs.

Freeze-drying is the most commonly used preservation method for poultry. This process carefully removes water from the bacterial culture, keeping the cells viable in a dry, stable state for long-term storage [229]. Advantages of this method include resistance to high temperatures during feed mixing and a longer shelf life, while maintaining bacterial viability after rehydration in the digestive tract [230].

Recent advances highlight the use of nanotechnology and advanced delivery platforms to enhance probiotic stability, bioavailability, and immune effects [231]. Nanoparticle-based encapsulation protects probiotic cells from heat, oxygen, and stomach acidity, ensuring higher survival rates and improved colonization of the gut [232]. Such formulations have been shown in 2025 trials to improve villus height, enhance mucosal immunity, reduce mortality, and support growth performance under commercial conditions [233]. Water-delivered microencap-sulated probiotics allow precise dosing, rapid gut delivery, and minimal loss during feed processing.

Regarding duration of administration, short-term supplementation (7–14 days) is often applied around critical periods such as post-hatch, feed transition, vaccination, or disease challenge to enhance immune responsiveness [234]. In contrast, continuous supplementation throughout the production cycle (e.g., 4–6 weeks in broilers or extended periods in layers) has been associated with more stable gut microbiota establishment, improved feed efficiency, and sustained immune modulation [15]. Early-life administration, particularly during the first week post-hatch, appears especially important for promoting immune organ development and long-term microbiota stability [235].

Dose–response studies generally indicate a positive response up to an optimal threshold, beyond which benefits plateau and, in some cases, excessive doses may disturb microbial balance [131]. This suggests a non-linear dose–response relationship rather than a simple “more is better” effect. Therefore, probiotic application should consider both minimal effective dose and economic efficiency, ideally supported by controlled trials or farm level performance monitoring [80].

The choice of probiotic dosage form should be tailored to the intended use, the age of the birds, environmental conditions, and the method of administration [236]. Using the right dosage form ensures the viability of the probiotic bacteria, optimal immunomodulatory effects, and maximizes the benefits for digestive health and poultry performance [237].