Growing flocks without antibiotics

Photo: Marcelo/Adobe Stock

Antibiotics have been used in human and animal health since the early 20th Century. Since their introduction, inappropriate use and overprescription has led to antibiotic resistance.¹ Antibiotic resistance can be transferred to humans from animals that have been treated with antibiotics, leading to outbreaks of dangerous infections. This has led to the FDA banning of most classes of antibiotics for use in livestock in 2019.²

The United States is the leading chicken producer in the world, and second only to China in chicken egg production. In a review of emerging issues in poultry farming, published in Poultry Science, the authors found that consumer awareness has led to the demand for chicken raised not only in an environmentally stable manner, but also in a way that promotes the animal’s welfare. This has led to the increase for more organic, cage-free poultry.²

Although chickens raised in these open-environment pastures have been deemed more ethical, they are also more susceptible to pathological bacterial contamination compared to conventional “factory farms.” This is because of the increased interaction with other chickens, and exposure to potential airborne pathogens. Since organic farms are not allowed to use antibiotics or synthetic chemicals or antimicrobials for therapeutic or preventative use, researchers are looking into other methods for preventing infections in chickens.²

Bacteriophages–viruses that only replicate in bacterial cells–are one of the most widely available methods of infection prevention against specific bacterial strains. Due to their specificity, they do not disturb the chicken’s natural microflora and can be administered via aerosols. Due to each bacteriophage’s specificity, the aerosol would need to contain a cocktail of different bacteriophages, this could lead to a larger increase in horizontal gene transfer.²

Vaccines are already used in protecting poultry from disease by preparing their immune defense mechanisms. However, like bacteriophages, vaccines are also highly specific and take significantly more time to develop and produce. While extremely successful at preventing disease, it is not a cost-effective method.²

The most promising option to date is using a substance called “synbiotics.” Synbiotics are defined as the combination of probiotics such as L casei and prebiotics found in food products like cacao and blueberries. Previous studies have shown that probiotics are more effective in producing their antimicrobial agents when in the presence of a prebiotic substance. Synbiotic preparations have also been shown to increase the population of beneficial bacteria in the gut microbiome.²

Synbiotics’ long-term effects are unknown, as are the best ways to deliver both the prebiotic and probiotic elements. While microencapsulation has proven moderately successful, more methods are in demand. Future studies on this method of microbial protection should investigate the mode of delivery that can ensure the survivability of probiotics while investigating the long-term effects of consistent synbiotic use.²

References

1. New Intermountain, Stanford study finds excess harm from commonly overprescribed antibiotics for patients resulting in widespread side effects. Intermountain Health. March 29, 2023. Accessed August 1, 2023. https://intermountainhealthcare.org/news/2023/03/new-intermountain-stanford-study-finds-excess-harm-from-commonly-overprescribed-antibiotics/#mediaContact
2. Tabashsum Z, Scriba A, Biswas D. Alternative approaches to Therapeutics and subtherapeutics for Sustainable Poultry production. Poultry Science. 2023;102(7):102750. doi:10.1016/j.psj.2023.102750