Beyond the gut health of poultry
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Dr K Rashbehari Singh
INTRODUCTION
In poultry, gut health refers to the overall well-being and functioning of the gastrointestinal tract (GIT) and it is important for maintaining the overall health and well-being of the birds. A healthy gastro-intestinal system is important for achieving maximum production potential of birds. Feed efficiency, nutrient absorption, and the overall immunity of the birds are improved in a healthy gut. Optimal nutrient absorption is ensured by a well-functioning digestive system and ultimately contributes to economic sustai- nability in poultry farming. With numerous different aspects, intestinal health is an extremely complex topic. Dysbiosis, mucosal barrier leakage and inflammation are three main and interrelated drivers of poor intestinal health.
GUT HEALTH
Gut health relies on the maintenance of the delicate balance between the host, the intestinal microbiota, the intestinal environment and dietary compounds and factors such as bird manage- ment, feed quality and the birds’ environment can significantly affect this balance. There is complete digestion of the feed and absorption of the nutrient components when gut health is optimal. On the other hand, if there is a disruption to the normal processes in the gut, incomplete digestion and absorp- tion of nutrients can occur, leading to malabsorption and gut imbalance. Gut health is at risk of being compromised if there is any imbalance in the gut environment, which can impact the health and performance of the birds. When digestion and absorption are not optimal, there is malabsorption of nutrients resulting in more nutrients being available to the small intestinal bacteria that can lead to an overgrowth of the bacterial population. A further consequence of malabsorption is the passing of proteins, sugars and fat into the caeca causing an overgrowth in the microbial population and a shift away from the beneficial fermentative bacteria.
IMPORTANCE OF GUT HEALTH
Gut health is key for overall performance, health and welfare of poultry birds. The main infectious causes that impair gut health in poultry are mainly from bacterial origin. The pathogens cause digestive disor- ders in poultry, often characterised by inflammation of intestinal walls, sloughing of enterocytes (intestinal cells) and shortening of villi.
The host benefits in different ways due to the pre- sence of gut microbiota consisting of beneficial bacteria. They expand the digestive capacity, produce essential nutrients, increase colonization and resistance against pathogenic intruders, and assist in detoxi- fication. The more diverse and richer the microbiome, the healthier the host. The gut microbiota depends on the microbial substrate preference coming from the host diet.
Digestion and absorption of nutrients are main functions of the gut, and the efficiency of feed digestion and absorption is directly proportional to the healthy intestine, more specifically intestinal villi. The longer the villi, the more the surface for absorption and healthier the microvilli, the more production of enzymes to break down the complex molecules. The enterocyte lining acts as physical barrier between intestinal lumen and blood. The cells are tightly sealed together called tight junctions, preventing bacteria and toxic substances from entering directly into blood and causing inflammation and leaky gut.
For both broiler and broiler breeder production and welfare, the efficient conversion of feed into its basic components for optimal nutrient absorption is vital. Gut health, an intricate and complex area combining nutrition, microbiology, immunology and physiology, has a key role to play. Digestion and nutrient absorption in birds are affected when gut health is compromised, and in turn, can have a detrimental effect on feed conversion leading to economic loss and a greater susceptibility to disease.
The intestinal barrier of the chicken, consisting of physical, chemical, microbial, and immunological factors distributed throughout different layers, contri- butes to its protection against pathogens, the colonization of commensal microorganisms, as well as the digestion and the absorption of nutrients. Gastrointestinal bacteria in poultry intestines ferment non-digestible carbohydrates to produce short- chain fatty acids (SCFAs) such as acetate, propionate, and butyrate, which serve as a crucial energy source for the host. Disturbances of the intestinal microbiota in poultry directly impact health, nutrient absorption, and production performance.
DIGESTION OF FEED
The feed enters the crop and stores there for a short period of time. In the crop, the feed is partially fermented by the resident bacteria. The feed then enters the proventriculus where it is mixed with acid and pepsin (an enzyme responsible for breaking down complex feed proteins into smaller peptide chains and then on to the gizzard. The gizzard acts like a grinding mill to break the feed into smaller particles and then it releases the feed into the small intestine once the feed particles are small enough. While the gizzard grinds the feed, it is mixed with the acid and enzymes secreted by the proventriculus.
The digestive process allows for the breakdown of whole proteins into smaller peptides which can then be digested in the small intestine into amino acids for absorption. Carbohydrates and fats are also broken down within the small intestine, so that they can be absorbed and used by the birds. By the time the digesta reaches the last part of the ileum, all the proteins, fats and carbohydrates should have been absorbed leaving behind the non-digestible components of the feed such as cellulose, non-starch polysaccharides etc. These materials are either passed out in faeces or taken up by the caeca where bacteria ferment them to form organic acids, short chain fatty acids and vitamins which the bird can absorb for extra nutrients. Chickens produce two types of droppings at the end of digestion, a caecal and a faecal which look very different.
IMMUNOLOGY OF GUT HEALTH
The GIT of poultry is considered the largest immune organ in the body, hosting approximately 70 – 80 % of all immune cells. This concentration of immune cells in the gut is crucial because the intestine is the primary point of entry for pathogens. The intestinal surface area is highly adaptable, often developing a larger capacity for absorption to match rapid growth of meat-type birds. The intestine has several specia- lized cells and a plethora of diverse microorganisms – the microbiome.
The gut is the first line of defense against pathogens that enter the body through the digestive system, and it is a critical component of the immune system. Chickens have a specialized immune system in the gut, known as gut-associated lymphoid tissue (GALT), which is a highly developed specialized mucosal immune system responsible for generating immune responses and maintaining intestinal health. The GALT includes Peyer’s Patches, which are clusters of immune cells widely scattered along the intestine, as well as the gut-associated lym-phocytes (GALs) that are found throughout the gut. These immune cells are responsible for recognizing and responding to pathogens that enter the gut.
Several different mechanisms are involved in the gut-mediated immune response in chickens, inclu- ding the activation of immune cells, the production of antibodies, and the release of inflammatory mediators. To help fight off the infection, the GALT and GALs play a crucial role by identifying and responding to pathogens, as well as activating other immune cells.
GUT MICROBIOME
The gut microbiome of broiler birds is a complex, dynamic ecosystem primarily composed of bacteria (over 90%), but also including fungi, archaea, protozoa, and viruses. This microbial community plays a critical role in nutrient digestion, immune system maturation, and protection against pathogens through competitive exclusion. Important bacteria like Lactobacillus are vital for gut health, with populations influenced by diet, age, and antibiotic usage. GIT is dominated by bacteria, with the highest density and diversity found in the caecum. Optimising gut microbiome is crucial for improving feed conversion ratios, reducing disease incidence, and ensuring efficient growth in broilers.
There are multiple interactions between the host (bird) cells, the intestinal environment, bacterial cells and feed components within the GI tract, emphasizing the extremely important role of gut microbiota.
DYSBIOSIS
Dysbiosis in broiler birds is an imbalance of intestinal microbiota, that causes intestinal inflammation, poor nutrient absorption, and reduced performance. This is caused by a disproportionate increase in certain gut microbes, infection with a pathogenic microbe, or by external factors such as environmental stress, antibiotic use, nutritional imbalances or poor management.
Clinical signs of dysbiosis include increased water intake, decreased feed consumption, poor growth rates, and, in severe cases, necrotic enteritis. Dysbiosis compromises the gut barrier function, leading to decreased weight gain, reduced feed conversion efficiency, and increased susceptibility to disease. Dysbiosis in broilers is managed by maintaining gut health through balanced nutrition, high-quality feed ingredients, rigorous bio- security, and environmental control such as stress reduction, proper ventilation/ litter management. Use probiotics , prebiotics, organic acids, and enzymes to stabilize microbiota. Prevent wet litter and ensure early and consistent access to feed and water.
CONCLUSION
Out of any food producing animal, maintaining the balance of good gut health is a key aspect of getting the best growth and Feed Conversion Ratio (FCR). The gut remains a highly complex area and many researchers have attempted to understand gut flora, gut function and gut immunity. Further complexity is added to maintain good gut health in poultry due to regional variations in poultry production, management styles, climate, disease challenge and feed raw materials. However, developing and maintaining gut health through good bird management practices is key to maintaining bird health, welfare and performance.
The writer is Member, Manipur State Veterinary Council, Imphal & Former Deputy Director (Extension Education), CAU, Imphal
INTRODUCTION
In poultry, gut health refers to the overall well-being and functioning of the gastrointestinal tract (GIT) and it is important for maintaining the overall health and well-being of the birds. A healthy gastro-intestinal system is important for achieving maximum production potential of birds. Feed efficiency, nutrient absorption, and the overall immunity of the birds are improved in a healthy gut. Optimal nutrient absorption is ensured by a well-functioning digestive system and ultimately contributes to economic sustai- nability in poultry farming. With numerous different aspects, intestinal health is an extremely complex topic. Dysbiosis, mucosal barrier leakage and inflammation are three main and interrelated drivers of poor intestinal health.
GUT HEALTH
Gut health relies on the maintenance of the delicate balance between the host, the intestinal microbiota, the intestinal environment and dietary compounds and factors such as bird manage- ment, feed quality and the birds’ environment can significantly affect this balance. There is complete digestion of the feed and absorption of the nutrient components when gut health is optimal. On the other hand, if there is a disruption to the normal processes in the gut, incomplete digestion and absorp- tion of nutrients can occur, leading to malabsorption and gut imbalance. Gut health is at risk of being compromised if there is any imbalance in the gut environment, which can impact the health and performance of the birds. When digestion and absorption are not optimal, there is malabsorption of nutrients resulting in more nutrients being available to the small intestinal bacteria that can lead to an overgrowth of the bacterial population. A further consequence of malabsorption is the passing of proteins, sugars and fat into the caeca causing an overgrowth in the microbial population and a shift away from the beneficial fermentative bacteria.
IMPORTANCE OF GUT HEALTH
Gut health is key for overall performance, health and welfare of poultry birds. The main infectious causes that impair gut health in poultry are mainly from bacterial origin. The pathogens cause digestive disor- ders in poultry, often characterised by inflammation of intestinal walls, sloughing of enterocytes (intestinal cells) and shortening of villi.
The host benefits in different ways due to the pre- sence of gut microbiota consisting of beneficial bacteria. They expand the digestive capacity, produce essential nutrients, increase colonization and resistance against pathogenic intruders, and assist in detoxi- fication. The more diverse and richer the microbiome, the healthier the host. The gut microbiota depends on the microbial substrate preference coming from the host diet.
Digestion and absorption of nutrients are main functions of the gut, and the efficiency of feed digestion and absorption is directly proportional to the healthy intestine, more specifically intestinal villi. The longer the villi, the more the surface for absorption and healthier the microvilli, the more production of enzymes to break down the complex molecules. The enterocyte lining acts as physical barrier between intestinal lumen and blood. The cells are tightly sealed together called tight junctions, preventing bacteria and toxic substances from entering directly into blood and causing inflammation and leaky gut.
For both broiler and broiler breeder production and welfare, the efficient conversion of feed into its basic components for optimal nutrient absorption is vital. Gut health, an intricate and complex area combining nutrition, microbiology, immunology and physiology, has a key role to play. Digestion and nutrient absorption in birds are affected when gut health is compromised, and in turn, can have a detrimental effect on feed conversion leading to economic loss and a greater susceptibility to disease.
The intestinal barrier of the chicken, consisting of physical, chemical, microbial, and immunological factors distributed throughout different layers, contri- butes to its protection against pathogens, the colonization of commensal microorganisms, as well as the digestion and the absorption of nutrients. Gastrointestinal bacteria in poultry intestines ferment non-digestible carbohydrates to produce short- chain fatty acids (SCFAs) such as acetate, propionate, and butyrate, which serve as a crucial energy source for the host. Disturbances of the intestinal microbiota in poultry directly impact health, nutrient absorption, and production performance.
DIGESTION OF FEED
The feed enters the crop and stores there for a short period of time. In the crop, the feed is partially fermented by the resident bacteria. The feed then enters the proventriculus where it is mixed with acid and pepsin (an enzyme responsible for breaking down complex feed proteins into smaller peptide chains and then on to the gizzard. The gizzard acts like a grinding mill to break the feed into smaller particles and then it releases the feed into the small intestine once the feed particles are small enough. While the gizzard grinds the feed, it is mixed with the acid and enzymes secreted by the proventriculus.
The digestive process allows for the breakdown of whole proteins into smaller peptides which can then be digested in the small intestine into amino acids for absorption. Carbohydrates and fats are also broken down within the small intestine, so that they can be absorbed and used by the birds. By the time the digesta reaches the last part of the ileum, all the proteins, fats and carbohydrates should have been absorbed leaving behind the non-digestible components of the feed such as cellulose, non-starch polysaccharides etc. These materials are either passed out in faeces or taken up by the caeca where bacteria ferment them to form organic acids, short chain fatty acids and vitamins which the bird can absorb for extra nutrients. Chickens produce two types of droppings at the end of digestion, a caecal and a faecal which look very different.
IMMUNOLOGY OF GUT HEALTH
The GIT of poultry is considered the largest immune organ in the body, hosting approximately 70 – 80 % of all immune cells. This concentration of immune cells in the gut is crucial because the intestine is the primary point of entry for pathogens. The intestinal surface area is highly adaptable, often developing a larger capacity for absorption to match rapid growth of meat-type birds. The intestine has several specia- lized cells and a plethora of diverse microorganisms – the microbiome.
The gut is the first line of defense against pathogens that enter the body through the digestive system, and it is a critical component of the immune system. Chickens have a specialized immune system in the gut, known as gut-associated lymphoid tissue (GALT), which is a highly developed specialized mucosal immune system responsible for generating immune responses and maintaining intestinal health. The GALT includes Peyer’s Patches, which are clusters of immune cells widely scattered along the intestine, as well as the gut-associated lym-phocytes (GALs) that are found throughout the gut. These immune cells are responsible for recognizing and responding to pathogens that enter the gut.
Several different mechanisms are involved in the gut-mediated immune response in chickens, inclu- ding the activation of immune cells, the production of antibodies, and the release of inflammatory mediators. To help fight off the infection, the GALT and GALs play a crucial role by identifying and responding to pathogens, as well as activating other immune cells.
GUT MICROBIOME
The gut microbiome of broiler birds is a complex, dynamic ecosystem primarily composed of bacteria (over 90%), but also including fungi, archaea, protozoa, and viruses. This microbial community plays a critical role in nutrient digestion, immune system maturation, and protection against pathogens through competitive exclusion. Important bacteria like Lactobacillus are vital for gut health, with populations influenced by diet, age, and antibiotic usage. GIT is dominated by bacteria, with the highest density and diversity found in the caecum. Optimising gut microbiome is crucial for improving feed conversion ratios, reducing disease incidence, and ensuring efficient growth in broilers.
There are multiple interactions between the host (bird) cells, the intestinal environment, bacterial cells and feed components within the GI tract, emphasizing the extremely important role of gut microbiota.
DYSBIOSIS
Dysbiosis in broiler birds is an imbalance of intestinal microbiota, that causes intestinal inflammation, poor nutrient absorption, and reduced performance. This is caused by a disproportionate increase in certain gut microbes, infection with a pathogenic microbe, or by external factors such as environmental stress, antibiotic use, nutritional imbalances or poor management.
Clinical signs of dysbiosis include increased water intake, decreased feed consumption, poor growth rates, and, in severe cases, necrotic enteritis. Dysbiosis compromises the gut barrier function, leading to decreased weight gain, reduced feed conversion efficiency, and increased susceptibility to disease. Dysbiosis in broilers is managed by maintaining gut health through balanced nutrition, high-quality feed ingredients, rigorous bio- security, and environmental control such as stress reduction, proper ventilation/ litter management. Use probiotics , prebiotics, organic acids, and enzymes to stabilize microbiota. Prevent wet litter and ensure early and consistent access to feed and water.
CONCLUSION
Out of any food producing animal, maintaining the balance of good gut health is a key aspect of getting the best growth and Feed Conversion Ratio (FCR). The gut remains a highly complex area and many researchers have attempted to understand gut flora, gut function and gut immunity. Further complexity is added to maintain good gut health in poultry due to regional variations in poultry production, management styles, climate, disease challenge and feed raw materials. However, developing and maintaining gut health through good bird management practices is key to maintaining bird health, welfare and performance.
The writer is Member, Manipur State Veterinary Council, Imphal & Former Deputy Director (Extension Education), CAU, Imphal