**1. Introduction**

Over recent years, the scientific community has expressed great concern about antimicrobial resistance (AMR), which has been recognized as one of the most serious global public health threats in this century [1]. Nowadays, most multilateral organizations focused on global health accept the use of antibiotics in animal intended for food production as one of the main drivers of AMR infections in human health, adopting national action plans that commit to reduce the indiscriminate use of antibiotics by their members [2–4]. These action plans propose many strategies to control this problem, particularly by encouraging reasonable and limited use of antibiotics in food animal production, particularly those that are considered of critical importance for both human and veterinary medicine. The World Health Organization (WHO) has issued a series of guidelines and resolutions in regard to the use of antimicrobial agents in animal production, among those that stand out being the overall reduction

in the use of all classes of antimicrobials, with the conditional recommendation not to use those that have been classified as critically important for human medicine, as well as the complete restriction for growth promotion and prevention of infectious diseases that have not yet been clinically diagnosed [5], for which some government regulatory agencies have taken action on the use of antibiotics for animal production, resulting in their total ban as growth-promoting agents [6, 7].

It could be expected that the total ban on the use of antibiotics as growth promoters will lead to a decrease in the levels of antibiotic resistance [8]. However, we cannot ignore some issues resulting from this ban, such as the increase in the incidence of bacterial infections which would also increase the use of other antibiotics at prophylactic or even therapeutic doses, accelerating the development of AMR in these pathogens and making it a worse scenario [9, 10]. In addition, some farming practices must be implemented to reduce the use of antibiotics in animal production, such as adequate animal vaccination, good hygiene and husbandry practices, higher animal welfare, and improved breeding programs, which implies an increase in production costs, and it is still not enough to completely reduce the risks of infection [11, 12].

Poultry is one of the most commonly exploited species worldwide, and a sector that continues to grow and industrialize in many parts of the world [13], so it was to be expected that a large part of the antibiotics used in animal production was destined to this industry [14, 15]. Antibiotics have been used in poultry production for therapeutic, prophylactic, or growth promotion purposes, especially in broiler chickens, which has resulted in huge profits for poultry producers [16].

Although it is a fact that the reduction or complete abolition in the use of antibiotics for poultry production would have a positive effect in the control of AMR and public health, this would also have negative economic repercussions, since production costs and, consequently, the prices of the final products, as well as the international trade of poultry products, would be affected [17, 18]. Furthermore, the antibioticfree production of poultry could imply public health problems caused by foodborne pathogens such as e *C. perfringens*, *E. coli*, *S. aureus*, *Campylobacter spp*., or *Salmonella spp*. [19–21] while increasing production costs caused by bacterial infections, along with the detriment in the health of the birds and the decrease of the productive parameters. Hence, the ban on the use of antibiotics for poultry production, as well as other increasingly popular trends, such as the growth of the organic products market, has forced poultry producers to find viable alternatives with similar benefits to antibiotics. For that, many specific alternatives have been evaluated and marketed, such as enzymes, prebiotics, probiotics, organic acids, dietary fiber, highly available nutrients, herbs, spices, essential oils, plant components, and vaccines [15].

Among all the available alternatives, prebiotics have proven to be promising alternatives for the poultry industry because they are able to pass through the digestive tract, which facilitates and supports the symbiotic relationship between the host and gastrointestinal tract (GIT) microbiota and results in health benefits for the birds [22–24]. Thus, this chapter exposes the use of prebiotics as feed additives in poultry, with emphasis on their beneficial effects on the microbiota composition, their ability to control pathogenic infections, positive changes in intestinal morphology, improved productive parameters, and immunomodulatory effects as possible mechanisms of action, which make them potential alternatives to avoid the use of antibiotics as growth promoters in the poultry industry.
