Probiotics as Alternative to Antibiotics in Poultry: Challenges and Prospects

Probiotics are “live microbial feed additives that benefit the host by enhancing gut microbial balance” (eubiosis). Probiotics can be bacteria, fungi, or yeasts, and their use in poultry has progressively expanded over the years due to the rising demand for antibiotic alternatives. Although several microorganisms have been assessed to be used as probiotics, certain species can fulfill the assessment criteria such as (i) Resistance to the digestive system conditions (acid and bile), (ii) Ability to colonize the gastrointestinal tract (GIT) and triggering pathogen displacement (competitive exclusion), (iii) Inhibition of the growth of potential pathogens by producing antimicrobial metabolites, and (iv) Modulation of the immune system. Indeed, probiotics increase nutrient utilization and performance and reduce foodborne pathogens. Several factors affect the extent, magnitude, and duration of probiotic efficacy, including bacterial species, GIT ecological niche occupancy, metabolic products, rearing conditions, the dose, the frequency of daily administration, timing of administration (before, during, and after a meal), method of delivery (fermented feed, orally via drinking water, in the feed), the viability of the probiotic bacteria, and the duration of administration (short term or longer term). In the present review, we shed light on the mechanism of action of probiotics and their use in poultry. Additionally, we highlight the main challenges and possibilities for overcoming breakdowns of probiotics application.