Role of Probiotics in the Control of Necrotic Enteritis in Poultry
Necrotic enteritis (NE) poses a significant challenge to the poultry industry, causing economic losses and impacting the overall health of flocks. The overuse of antibiotics and changes in management practices have contributed to the rise of NE. In recent years, there has been growing interest in the use of probiotics as a natural and sustainable strategy for preventing and controlling necrotic enteritis in poultry. This article explores the role of probiotics in mitigating the impact of NE and promoting the gut health of poultry.
Necrotic enteritis caused by Clostridium perfringens is an acute disease of 2-4 weeks old broiler chickens, producing high mortality. The disease is routinely controlled by antimicrobial drugs, antibiotic growth promoters and ionophores anticoccidials. But this practice has recently come under greater scrutiny due to rise and spread of antibiotic resistant bacterial strains. Thus, suitable alternative prophylactic measures against NE have been warranted. In the present study, role of probiotics in the control of NE is explored.
Poultry production in India has become increasingly specialized and integrated into a dynamic industry of major national and international importance. Poultry production has played a pivotal role in increasing source of income and employment generation for the educated unemployed youth. To achieve high levels of economic efficiency, poultry are raised under intensive system in densely populated flock. Due to the intensification, the birds face lots of stress, which lead to imbalance in the intestinal microflora and lowering of body defense mechanisms, making them vulnerable to many diseases. Among the prevailing pathogens, intestinal pathogens are a major cause of death, disease and poor performance in poultry. Clostridium perfringens is one of such pathogens causing necrotic enteritis in poultry. Necrotic enteritis (NE) caused by massive proliferation of C. perfringens in the small intestine of the chicken has been a persistent problem in commercial poultry, especially in rapidly growing broiler chickens. It is an acute disease of 2-4 wk old broiler chickens, causing high mortality and poor feed conversion ratio. Normally, the number of C. perfringens in the intestine is low (about 104 cfu/g of digesta). The disease occurs when high numbers of bacteria coincide with a damaged intestinal mucousa (Alsheikhly and Truscott, 1977). The disturbances in normal intestinal microfolora may cause rapid proliferation of C. perfringens, increasing bacterial numbers the range from 107 to 109 cfu/g of digesta resulting in toxin production (Kondo, 1988). Necrotic enteritis is routinely controlled by incorporation of antimicrobial drugs, antibiotic growth promoters and ionophore anticoccidials. Johnsson et al. (2004) reported that all strains, regardless of origin, proved inherently susceptible to ampicillin, narasin, avilamycin, erythromycin and vancomycin. In spite of these, considering the public concern about the threat of antibiotic resistant pathogens, the European Union banned avoparcin in January, 1997, Ardamycin in January, 1998 and further four antibiotics bacitracin, virginamycin, tylosin and spiramycin in December, 1998. Ban of remaining antibiotics and antibiotics growth promoters may be in the near future (Immerseel et al., 2004). The use of coccidiostats of ionophore type, which is one of the main tools to control NE are also forbidden in the year 2012. Unfortunately, due to the withdrawal of antimicrobial drugs, antibiotic growth promoters and ionophore anticoccidials, NE is expected to become more widespread. This phenomenon has already been observed in several poultry raising countries, where restrictions and limitations on the use of growth promoting and prophylactic antibiotics in chicken feed have led to an increase in the prevalence of NE (Wise and Siragusa, 2005). Hence, possible alternate strategies for control of NE in the ‘post – antibiotic’ were suggested. This includes probiotics, prebiotics, organic acids, enzymes, hen egg antibodies, bacteriophages and vaccination. (Dahiya et al., 2006). The term direct-fed microbials or probiotics has been defined as a “live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance” (Fuller, 1999). Probiotics are intended to modify the gastrointestinal microflora in such a way that bacterial activities advantageous to the host are stimulated and those adverse to the host health are suppressed (Netherwood et al., 1999; Simmering and Blaut, 2001). A number of studies have reported a potential benefit of culture of caecal material on NE in broiler chickens including reduced mortality and reduced caecal colonization of C.perfringens (Elwinger et al., 1992). Hofacre et al. (1998) challenged broiler chickens experimentally with C. perfringens and observed that normal gut flora products reduced gross intestinal lesions and improved feed efficiency in broiler chicken. Craven et al. (1999) reported a reduction in C. perfringens colonization and decreased incidence of necrotic enteritis in chickens treated with normal gut flora, together with increased slaughter yield. In a field study, Kaldhusdal et al. (2001) found that posthatch use of flora prepared from adult birds was associated with delayed intestinal proliferation of C. perfringens, delayed appearance of NE gross lesions and better production performance at slaughter. Maintenance of a stable gut flora was essential to prevent dysbacteriosis, a general overgrowth of the intestinal microflora, which may predispose to NE by reducing oxygen tension to a level favourable for C. perfringens proliferation (Schuring and Gills, 2001) Studies regarding the protective effects of probiotic strains against C. perfringens in chickens are limited. Fukata et al. (1988) and Fukata et al. (1991) reported a very low mortality in chicks inoculated with L. acidophilus or S. faecalis and then challenged with C. perfringens compared with a 50 per cent mortality rate in germ free chicks and no mortality in conventional birds. They also observed a suppression of alpha toxin production when chick intestinal contents were cocultured with C. perfringens. Hofacre et al. (1998) observed that a commercial probiotic product reduced gross lesions of necrotic enteritis in chickens, but the protection was far less than that conferred by a normal gut flora preparation. Mortality due to necrotic enteritis was significantly reduced from 60 to 30 per cent in experimentally challenged broilers when they were treated with a defined lactic acid bacterial culture at day 1 of age (Hofacre et al., 2003). In this experiment, feed conversion was decreased in the group that was given lactobacilli, but weight gain was not affected. La Ragione and Woodward (2003) reported that when chickens of 1 and 20-day-old were challenged with 109 spores of Bacillus subtilis strain and infected 24 h later with 105 cfu of C. perfringens, colonization and persistence of C. perfringens was suppressed. Boobalan, (2006) reported that addition of probiotics in the feed resulted in increased weight gain, reduced mortality and reduced C. perfringens count in the intestine on NE induced birds. Reports of immunomodulation effect of probiotics against NE are scanty. However, immunomodulation effect of probiotics for other pathogens is available. Koenen et al. (2004) reported that Lactobacillus strain has different effect on the GI tract and immune system depending on the type, genetic-make up and age of the chicken. Though the magnitude of the effects per animal is limited, non specific enhancement of the immune system might support health of the flock in a very inexpensive way. Better effect of multistrain probiotics than single strain probiotics on immune response of broiler chicks vaccinated against avian influenza virus (Ghafoor et al., 2005). Kannan et al. (2005) reported that dietary supplementation of L.sporogenes had significantly improved the immune response against Ranikhet disease in broilers at 28 and 49 days of post vaccination.
Understanding Necrotic Enteritis
Necrotic enteritis is caused by the bacterium Clostridium perfringens, particularly certain strains that produce potent toxins. The disease is often associated with compromised gut health, intestinal damage, and predisposing factors such as coccidiosis. The symptoms range from mild forms with reduced growth rates to severe cases involving necrosis of the intestinal lining.
The Role of Probiotics
Probiotics are live microorganisms that confer health benefits when administered in adequate amounts. In the context of poultry, probiotics primarily consist of beneficial bacteria such as Lactobacillus and Bacillus species. The administration of probiotics aims to restore and maintain a balanced microbial population in the gut, promoting a healthy gut environment.
Mechanisms of Probiotic Action Against Necrotic Enteritis
- Competitive Exclusion: Probiotics compete with pathogenic bacteria for adhesion sites and nutrients in the intestinal mucosa. By occupying these sites, probiotics help prevent the colonization of harmful bacteria like Clostridium perfringens.
- Production of Antimicrobial Substances: Some probiotic strains produce antimicrobial substances, such as organic acids and bacteriocins, that inhibit the growth and activity of pathogenic bacteria.
- Modulation of Immune Response: Probiotics have immunomodulatory effects, enhancing the innate and adaptive immune responses of poultry. This can contribute to the defense against bacterial infections, including Clostridium perfringens.
- Improved Gut Barrier Function: Probiotics strengthen the intestinal barrier, reducing the likelihood of pathogens crossing into the bloodstream and causing systemic infections. This is particularly relevant in preventing the damage associated with necrotic enteritis.
- Stimulation of Mucus Production: Probiotics can stimulate the production of mucus in the intestinal lining, creating a protective layer that acts as a physical barrier against pathogenic invasion.
Selecting Effective Probiotic Strains
The efficacy of probiotics in controlling necrotic enteritis depends on the selection of appropriate strains. Consider the following factors:
- Species and Strain Specificity: Different probiotic strains exhibit varying effects. Choose strains with proven efficacy against Clostridium perfringens.
- Survival and Colonization: Probiotics must survive the harsh conditions of the gastrointestinal tract and effectively colonize the gut to exert their beneficial effects.
- Safety and Compatibility: Ensure that selected probiotic strains are safe for poultry consumption and compatible with other management practices.
Practical Application in Poultry Farms
- Early Intervention: Probiotics are most effective when introduced early in the life of poultry. Incorporate them into the feeding program during the critical periods of gut development.
- Regular Supplementation: Maintain a consistent and regular supplementation of probiotics to support continuous gut health and resilience.
- Integrate with Other Management Practices: Probiotics should complement good management practices, including biosecurity measures, proper nutrition, and hygiene.
- Monitor and Adjust: Regularly monitor the health and performance of the flock. If necessary, adjust the probiotic formulation or dosage based on observed results.
Conclusion
Probiotics offer a promising and sustainable approach to controlling necrotic enteritis in poultry. By understanding the mechanisms through which probiotics act and selecting appropriate strains, poultry farmers can enhance gut health, improve resistance to infections, and ultimately reduce the impact of necrotic enteritis. Integrating probiotics into holistic management practices contributes to the overall well-being and productivity of poultry flocks, fostering a healthier and more resilient poultry industry.
Compiled & Shared by- This paper is a compilation of groupwork provided by the
Team, LITD (Livestock Institute of Training & Development)
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