Gut Health Management Strategies In Antibiotic Free Poultry Production

Gut Health Management Strategies In Antibiotic Free Poultry Production

Vaibhav Kr. Singh, Pankaj Kr. Shukla, Amitav Bhattacharyya and Ankit Sharma

Department of Poultry Science, DUVASU, Mathura, Uttar Pradesh 281001 India

The global poultry production continues togrowespeciallyinAsia.Poultrysectoris presently confronted with new array of challenges such as global food security, climate change, emerging infectious diseases,regulatorybanofantimicrobials, high-intensity production conditions and waste management. The World Health Organization (WHO) has warned that superbugs are reaching dangerous levels worldwide, a problem that is exacerbated by the overuse and abuse of antibiotics. The WHO has specifically called on individuals, healthcare professionals, policy makers and agricultural industries tomakechangestopreventthespreadof antibioticresistance. Antimicrobial resistance is a complex, multifaceted and urgent global health problem. There is an increasing concern about the emergence of multidrug resistant superbugs. This urgent threat requires implementation of a multifaceted strategy that has been articulated in the past few years. It is well established that antimicrobials in animal feed enhance feed efficiency, promote animal growth and improve the quality of animal products. But, resistance development in bacterial populations and hence consumer demand for products free of antimicrobial residues have prompted efforts to develop alternatives that can replace antimicrobials without causing loss of productivity or product quality (Morgan, 2017). The biggest stumbling block in antibiotic free (ABF) system is preventing necrotic enteritis (NE) without use of antibiotics in feed medication. Nowadays there is widespread interest in using in-feed nutraceuticals such as prebiotics, probiotics, organic acids and plant extracts as alternatives to antimicrobials to create a healthy gut and to prevent andtreatentericinfections.

Elements of gut health

Maintenance of optimal intestinal function (gut health) is dependent on three interdependent components: (1) immune system, (2) microbiota and (3) nutrition, which influence host physiology and metabolism.

Challenges associated with antibiotic free (ABF) poultry production Health challenges and Economic challenges

One of the key barriers to complete withdrawal from antimicrobial use in poultry is necrotic enteritis (NE). Clinical NEleadstosuddendeath,withmortality rates of up to 50% (Lee et al., 2011), but the subclinical form of the disease is morefinanciallydevastatingbecausethe lack of obvious symptoms means that there is delayed commencement of effective treatment, resulting in substantiallossinflockperformanceand reducedfeedefficiency. In an effort to minimize the loss of performance caused by removing antimicrobials, many producers may increase the floor-space allowance per bird, for example, from 0.23m2/bird to 0.27m2/bird to provide enhanced comfort to the birds. Thus, more poultry houses will be required and birds will need to be raised for longer, which will reduce the number of placements per year. The demand for additional feed resources and more drinking water will cause increase price for rearing.

Novel strategies to control gut health without antibiotic supplements

Substances that are used as alternatives to antimicrobials are generally unable to reduce microbial load and thus do not promote growth by mechanisms similar to those by which antimicrobials increase growth. But they promote GI tract health by mechanisms such as altering the pH, maintaining protective mucins (Brownlee et al., 2003), selecting for beneficial organisms and against harmful pathogens, enhancing fermentation acids (Khan and Iqbal, 2016), improving nutrient uptake and increasing humoral immune response (Sugiharto, 2016).

Nutritional strategies Diet composition

Different bacterial species have different substrate preferences and growth requirements; thus, it is the chemical composition of the digesta and digestibility of feed components that determine the composition of the gut microbial community. Apajalahti et al. (2004) who observed that broilers fed corn and sorghum-based diets had increased numbers of Enterococcus, broilers fed barley-based diets had increased numbers of Lactobacillus, broilers fed oat-based diet had enhanced growth of Escherichia and Lactococcus and broilers fed rye-based diets had increased the number of Streptococcus. Bacterial proliferation can be partly prevented by formulating diets based on digestible amino acids. A potential strategy is to feed low-protein diets supplemented with synthetic amino acids (Hilliar et al., 2017).

Feeding protein meals with poor digestibility due to improper heat processing result in increased production of toxic metabolites via proliferation of putrefying bacteria, such as the highly proteolytic C.perfringens.

Organic acids and fatty acids

Since organic acids have strong bacteriostatic effect, they are able to reduce the negative effects of zoonotic Salmonella. The impact of organic acids on lowering chyme pH and on gut morphology may also aid towards supporting health by enhancing protein digestion and absorption (Van Immerseel et al., 2006).Decreasing gut pH can enhance resistance to enteric diseases because clostridia and pathogenic bacteria do not grow at low pH. Volatile fatty acids and organic acids can manipulate the pH of the intestinal environment and prevent pathogens from attaching to the brush border of the intestinal lining. Saki et al. (2012) stated that supplementation with o rg a n i c a c i d s e n h a n c e d t h e concentration of lactic acid bacteria which cause reduction in pH of ileum and caeca so it causes decrease in intestinal Enterobacteriaceae and Salmonella counts. Polyunsaturated fatty acids (PUFAs), including n-3 and n-6 fatty acids enhances immune response. Maroufyan et al. (2012) reported that if birds have been fed n-3 PUFAs (from tuna, sunflower and palm oil), it cause increased spleen weight, antibody titres for infectious bronchitis disease (IBD) and Newcastle disease (NCD), interleukin-2 and interferon-g concentration in birds. He et al. ( 2 0 0 7 ) o b s e r v e d t h a t l o w concentrations of conjugated linoleic acid promoted growth of the thymus and bursa, stimulated T lymphocyte proliferation and elevated antibody production in chickens.

Probiotics and Prebiotics

Bischoff et al. (2014) reported that mucins and glycoproteins protect the absorptive site of the intestinal brush border from abrasion from feed stuffs, bacteria colonisation and toxins. Mucin is secreted by goblet cells in response to damage to the absorptive surface of the gut. The glycoproteins of gut mucins bind to and reduce colonisation of pathogens, by acting as alternative binding sites to receptors on host enterocytes (Schmidt et al., 2003). The dietary probiotic increased the proportion of Lactobacillus species in the ileum and significantly enlarged the goblet cell “cup” area throughout the small intestine. Expression of mucin mRNA and the levels of mucin glycoprotein were greater in the jejunum of the probiotic-fed chicks (Smirnov et al., 2005). The presence of an alternative substrate to mucins in the form of dietary prebiotics could reduce the likelihood of bacterial damage to mucins.

Probiotics

Probiotics are cultures of living organisms that enhance stability of resident microbiota and prevent growth of pathogens. Probiotics produce molecules with antimicrobial activities that either target specific pathogens or inhibit adhesion of pathogens or pathogenic toxin production (Pan and Yu, 2014). As well as maintaining a healthy bacterial balance via competitive exclusion and antagonism, probiotics also potentially promote gut integrity, modulate the immune system, increase digestive enzyme activity, reduce bacterial enzyme activity and ammonia production and neutralise enterotoxins (Sugiharto, 2016). Yeasts are promising candidates for replacing antimicrobials because of their numerous and diverse biological activities and antagonistic activities towards pathogenic bacteria and fungi. These activities include competitive exclusion, acidification of growth m e d i u m , t o l e r a n c e o f h i g h concentrations of ethanol, secretion of enzymes that degrade bacterial toxins, preventing adhesion to epithelial cell walls and release of antimicrobial compounds such as myocins and antibacterial compounds. Many species of Bacillus show antagonistic activity against Clostridium perfringens. Knap et al. (2010) observed that feeding Bacillus licheniformis improved performance and reduced mortality in necrotic enteritis infected birds and Bacillus subtilis spores suppressed colonisation and persistence of Clostridium perfringens in 20-day old chicks (La Ragione and Woodward, 2003).

Prebiotics

Commonly used prebiotics in poultry are oligosaccharides, such as fructooligosaccharides (FOS), mannanoligosaccharides (MOS), xylooligosaccahrides (XOS), galactooligosaccharides and inulin. Different prebiotics have different mechanism of action , for example both prebiotics MOS and FOS are beneficial to enteric health, but FOS feed the beneficial bacteria, competitively excluding colonisation of pathogens and hindering binding of pathogenic bacteria to the intestine, whereas mannanoligosaccharides (MOS) act as receptor analogues for pathogens and bind to the pathogens, resulting in their elimination from the digestive tract with the digesta flow and enhanced resistance to enteric pathogens. G a n g u l y ( 2 0 1 3 ) s t a t e d t h a t administration of prebiotics causes increased short-chain fatty acid (SCFA) production, recovering some of the energy lost from competition with bacteria and increasing intestinal acidity which contributes towards suppression of pathogenic organisms. Prebiotics are also thought to enhance immune response by directly interacting with gut immune cells or colonising beneficial microbes and their products that

interact with immune cells, resulting in rapid clearance of pathogens from the gut (Kim et al., 2011).

Phytogenics feed additives

Phytogenic effects have been proven in poultry for feed palatability and quality (sensory aspects), growth performance, reduced mortality, gut function and nutrient digestibility (improved growth), gut microflora (less diseases of the GIT, improved growth, reduced mortality), immune function and carcass meat safety and quality (reduced microbial load, improved sensory (Grashorn, 2010). The mechanisms by which they exert their beneficial effects include disrupting the cellular membranes of microbes and pathogens, increasing hydrophobicity of microbial species, stimulating growth of beneficial bacteria and acting as immunostimulatory substances (Windisch and Kroismayr, 2007). A body weight gain (g/bird) was found to be significantly (p<0.05) higher in 1% garlic and 1% ginger supplemented group as compare to control and garlic and ginger mixture supplemented group (Karangiya et al., 2016). Essential oils such as cavacrol from oregano can supress bacterial proliferation and reduce microbial load (Ri et al., 2017). They also display anticoccidial properties by increasing the turnover of the gut lining, which prevents coccidial attack.

Enzyme supplementation

Enzyme Xylanase cleave the internal beta-xylosidic glycosidic linakges of linear xylan chains to xylo-oligosaccharides (Jommuengbout et al., 2009) a n d p r o d u c e a m i x t u r e o f arabinosesubstituted xylo-oligosaccharides (arabinoxylanoligosaccharides, AXOS) and nonsubstituted xylooligosaccharides (XOS). Thus, the key outcomes of xylanase application include production of XOS that can be utilized more efficiently, endogenous digestive enzyme access to cell contents is improved, availability of indigestible substrates for microbial growth is lessened, digesta viscosity is decreased leading to reduced microbial populations in the upper tract and there is reduced loss of endogenous amino acids through modifications to pancreatic amylase and mucin secretion (Cowieson and Bedford, 2009). The resulting product xylo-oligomers also have prebiotic properties. Xylooligomers fascilitate proliferation of beneficial bacteria and are detrimental to the growth of non-beneficial bacteria.

Xylanase

Diet composition is a major contributor, pa r t i c u l a r l y d i e t s w i t h h i g h concentrations of indigestible watersoluble NSPs, suggesting that proliferation of C. perfringens could be partly mitigated using NSP-degrading enzymes. Liu et al. (2012) observed that xylanase supplementation alleviated impairment of the intestinal mucosa barrier induced by a C. perfringens challenge. Numbers of Coliforms and Salmonella in the ileum was reduced as a result of xylanase supplementation (Nian et al., 2011).

Phytase

Since phytic acid is antinutrients that diminish digestion which results in significant quantities of starch and protein enter the large intestine and stimulating putrefying bacteria and reducing gut health. Application of phytase has a direct impact on microbiota and hence improves gut health. Phytase increases protein digestibility and reduces endogenous losses, which limits protein supply to the hind gut. Dahiya et al. (2007) observed that undigested protein substrates act as predisposing factors for dysbacteriosis, particularly necrotic enteritis (NE), suggesting that phytase could possibly alleviate the prevalence and severity of NE.

Management strategies

Nutritional strategies alone are unable to overcome problems associated with the removal of antimicrobials because management also needs to be improved. Management strategies that can be used to improve gastrointestinal health include maintenance of dry litter by decreasing stocking density, increasing rate of ventilation and depth of shavings, heightened focus on sanitation of drinking water to minimise bacterial contamination, frequent removal of dead birds to prevent c a n n i b a l i s m a n d b a c t e r i a l contamination and good biosecurity practices to minimise physiological stress and reduce the potential for disease.

Conclusion:

Switching to an antibiotic free program is going to require a shift in the paradigm. The gut microbiome, immune system and nutrition are important integral parts for gut health. It is, however, clear that an appropriate gut microbiome, immune system and nutrition are all essential for optimum intestinal health and help in increase animal productivity. Feed additives like probiotics, prebiotics, enzymes, phytogenics and organic acids play a vital role in beneficially altering gut microbiota and improving intestinal integrity, physiology and immunology. A combination of nutritional strategies and management strategies can be used to achieve good gut health. No single alternative may be as effective as antimicrobials. Enzymes reduce substrate availability for microbial growth and influence the microbial ecosystem in the small intestine and caeca. Enzymes are also help in improvement of nutrients absorption. Molecular-microbiology techniques are an important component of research in this field and for quantifying beneficial and detrimental microbial populations. r