The Government of India recently issued a comprehensive ban on the use of antibiotic growth promoters (AGP) in layer feed, as stated in a notification published on February 27, 2023 (GOI, 2023). This move comes in response to the presence of antibiotic residues in animal-based food and the subsequent adverse effects on human health, particularly regarding antimicrobial resistance (AMR). Recognizing the urgency of the matter, India had already officially banned the use of AGPs with a withdrawal period back in 2012. AMR poses a significant concern for both animal and human health and has become a pressing global issue. Several countries took action against AGP use in the late 19th century, acknowledging its threat to human health. The countries which have banned AGP use in feed are listed in the table 1.
Table 1. Countries imposed ban on use of antibiotic growth promoters
Sr. No.
Country
YearAGP use restricted from
Remarks
Sweden
1986
Ban of sub-therapeutic AGP in feed
European Union
1997
Avoparcin banned
Denmark
1998
Sub-therapeutic in feed AGP banned
Holland
1998
Olaquindox banned
Switzerland
1999
Sub-therapeutic in feed AGP banned
Philippines
2000
Olaquindox, carbadox, nitrofurans and chloramphenicol banned
European Union
2006
Complete ban on sub-therapeutic AGP used in feed
Thailand
2006
All AGP banned in line with EU
Bangladesh
2010
All AGP banned in new feed act
South Korea
2011
All AGP banned
India
2012
Official ban with AGP withdrawal periods
Japan
2013
Monitoring by WHO on ban of AGP use
Canada
2014
Elimination of preventive use of category I antibiotics
United States of America
2017
Official AGP ban
China
2020
Official AGP ban
Despite the ban on AGP use in animal feed, there is still a considerable use of antimicrobials in food animal production. China (23%), the United States (13%), Brazil (9%), India (3%), and Germany (3%) are the top five consumers of antimicrobials for food animal production. Globally, India accounts for 3% of global consumption and ranks among the highest consumers worldwide. Penicillins, tetracyclines, and quinolones are the most widely used antibiotics globally, with higher usage in countries with meat-heavy diets. The use of antimicrobials in animal feed is projected to increase by 82% in India by 2030, with a specific tripling in their use in chickens.
The use of antibiotics in poultry began decades after the discovery of penicillin in 1928, primarily to treat parasitic and bacterial infections and enhance growth efficiency. Sir Alexander Fleming, the discoverer of penicillin, warned in a 1945 interview with the New York Times about the potential consequences of misusing penicillin, stating that “microbes are educated to resist penicillin.” Antimicrobial substances, produced by microorganisms, existed long before their use as medicinal drugs. These substances were created by microorganisms to kill other microorganisms, establishing a foundation for their own survival and propagation. This concept aligns with the principles of survival of the fittest, making it unsurprising that antimicrobial resistance has likely existed for as long as bacteria have. Bacteria exposed continuously to antimicrobials develop strategies for survival, and the development of resistance is one such strategy. While antibiotic resistance is a natural phenomenon, the misuse of antibiotics in both humans and animals accelerates the process, as emphasized by the World Health Organization (WHO). Continuous antibiotic use for enhanced production and growth efficiency exposes resident bacteria to these antimicrobials for prolonged durations, leading to antibiotic resistance.
Originally, it was believed that acquired resistance in bacteria only occurred through mutation in existing genes, confining the resistance trait to the mutant clone and limiting the spread of resistance to that clone (vertical transmission). However, in the 1960s, it was demonstrated that resistance could also develop through the acquisition of existing genes. In this case, the resistance trait, facilitated by mobile genetic elements, can spread to other bacterial clones, bacterial species, and even other genera (horizontal transmission) (Amabile-Cuevas and Chicurel, 1992).
Bacteria’s highly adaptable nature enables them to develop resistance to existing antibiotics, leading to a concerning cycle where the search for more potent antibiotics becomes increasingly expensive. Without intervention, the rise of superbugs poses a significant threat to human health, causing millions of deaths annually, with the numbers still rising.
AMR becoming the major threat predicting it will be the cause of highest deaths in 2050.
Review on antimicrobial resistance (2016).
Achieving antibiotic-free poultry production is not an easy task. Once AGPs are banned there are several challenges that need to be addressed in the future. Some of these challenges include: 1) preventing birds’ exposure to infectious agents, 2) effectively treating disease occurrences, and 3) controlling infectious diseases through immunological means. Avoiding exposure to infectious agents is extremely challenging. Post-outbreak treatments have variable effectiveness, depending on different physiological parameters and environmental conditions, but are generally less effective than preventive control. Immunological methods to control infectious diseases have recently gained attention as an ideal way to safeguard against subclinical infections. However, there has been limited success in protecting animals against bacterial pathogens that affect the intestinal and respiratory tracts using these methods.
Certain common checkpoints are affected when transitioning to antibiotic-free poultry production, such as poor gut health, reduced bird immunity, and decreased growth performance.
1. Gut health: The gut is a vital organ for nutrient utilization and overall health. A healthy gut involves more than just the absence of clinical diseases; it is about sustainably producing birds that can reach their full genetic potential. The absence of AGPs leaves birds more susceptible to gut health issues.
2. Poultry immunity and growth performance: Another challenge when transitioning from traditional to antibiotic-free poultry production is poultry diseases, particularly enteric diseases like coccidiosis and necrotic enteritis (NE), caused by species of Eimeria and Clostridium perfringens, respectively. It is also essential to consider viral challenges that may lead to secondary bacterial issues, taking advantage of the weakened immune system. In addition to diseases, other stressors such as feed, water, environmental factors, and behavior can negatively impact overall poultry health, growth, and immune function. Significant stressors or the cumulative effect of multiple small stressors, combined with low, moderate, or high disease challenges, can lead to problems. In such cases, the bird’s natural immunity may not be sufficient to manage the threats, highlighting the importance of preventive rather than reactive measures.
Several alternatives to antibiotics have been developed, tested, and are still being researched. Some of these alternatives show promising results, while others are only moderately effective.
A. Probiotics: Probiotics, also known as direct-fed microbials (DFMs), are live microorganisms that, when administered in adequate amounts, confer health benefits on the host according to FAO/WHO (2001) classification. Probiotics used in poultry include genera such as Lactobacillus, Streptococcus, Bacillus, Bifidobacterium, Enterococcus, Aspergillus, Candida, and Saccharomyces (Kabir, 2009). Probiotics can enhance host health in various ways, such as producing metabolites like lactic acid, modifying microbial metabolism, and improving cell integrity of the epithelium (Yaqoob et al., 2021). Unlike prebiotics, probiotics are microorganisms that can alter host health by colonizing the gastrointestinal tract (GIT) and providing a more balanced microbiota (Murate et al., 2015). The benefits of probiotics include improved performance, modulation of the intestinal microbiota, pathogen inhibition, enhanced intestinal integrity, immunomodulation, and improved microbiological and sensory characteristics of broiler meat (Alagawany et al., 2021; El-Saadony et al., 2021). The efficacy of probiotics is not specific, and the results vary depending on the quality of feed and water.
B. Essential Oils: Essential oils are derived from plants through water and/or steam distillation, and they possess valuable properties such as antimicrobial, antiviral, antioxidant, and antiparasitic capabilities (El-Tarabily et al., 2021). Many plant sources of essential oils have been studied for their efficacy as feed additives. For example, Tecnaroma Herbal Mix PL essential oil blend, containing herbs such as thyme, basil, and oregano, was supplemented in increasing amounts in broiler chickens (Khattak et al., 2014). The addition of essential oil positively impacted avian performance and carcass characteristics (Khattak et al., 2014). Essential oils have the ability to reduce pathogen levels, such as gram-negative E. coli and Salmonella bacteria, in the gut. However, bacteria can gradually adapt to these molecules and become resistant.
C. Organic Acids: Organic acids are weak acids that do not completely dissociate in the presence of water. Prominent types include carboxylic acids such as lactic acid, propionic acid, acetic acid, formic acid, sorbic acid, citric acid, oxalic acid, uric acid, and butyric acid. Organic acids are not antibiotics but, when used in conjunction with excellent nutrition, management, and biosecurity practices, they can help maintain intestinal health in poultry, leading to improved livability, feed conversion ratios, weight gain, live weight, and immunological responses (Adil et al., 2011). Each type of organic acid has unique properties and can be used for different purposes in poultry production. Like essential oils, continuous use of the same organic acids can lead to bacterial resistance over time.
D. Phytobiotics: Phytobiotics include plant extracts and compounds from herbs and spices, offering multiple benefits such as antimicrobial properties and immune support. Herbal extracts and spices play a significant role in improving health and productivity in poultry (El-Saadony et al., 2021). The positive impacts of plant extracts or active substances in bird feed may involve stimulating appetite, increasing feed intake, enhancing endogenous digestive enzyme production, stimulating immunity, and having antiviral, antibacterial, anthelminthic, and antioxidant activities. Identifying the active compounds and maintaining their concentration in the final product pose challenges. Often, commercially available products lack specific information about the key molecules within the plant extracts or compounds that contribute to their efficacy. Consequently, consistent results from such compounds are difficult to guarantee.
E. Bacteriophages: Bacteriophages have recently gained commercial importance in food animal production for bacterial control. Bacteriophages are viruses much smaller than bacteria that kill bacteria by injecting their genetic material into bacterial cells, allowing them to replicate and multiply inside the bacterial cells before causing cell lysis. This process destroys the bacterial cell, preventing the possibility of adaptation or the transfer of information for developing resistance. One of the key advantages of bacteriophages is their species specificity for attachment to bacteria. This allows bacteriophages to selectively kill pathogenic bacteria while allowing beneficial bacteria to proliferate, promoting better gut health and maintaining natural pH and microbial balance. Bacteriophages have no residual effects in the final product and do not cause toxicity. Bacteriophages continue to increase in population until the last pathogenic bacteria are eliminated.
In my opinion, when selecting a sustainable solution for antibiotic-free poultry production, the following qualities should be considered in the product:
Natural or organic origin
pH and temperature stability
Selective destruction of pathogenic microbial species
