Gut health has become a critical topic in the poultry industry, with information and discussion resonating in conferences, industry publications, and agricultural outlets. At its core, gut health, as per Bedford and Apajalahti (2022), signifies intestines that are fit for purpose, ensuring sustained nutrient absorption and gastrointestinal robustness.
Numerous feed additives, including antibiotics, have been suggested to enhance gut health. Using prophylactic (preventive) antibiotics, like ionophores, chemical coccidiostats, and Antibiotics as Growth Promoters (AGP), has proven effective in shielding chickens from intestinal diseases such as coccidiosis, necrotic enteritis, and dysbiosis (imbalance in the microbiota). Recently, the poultry industry has honed its attention on gut health due to escalating concerns about antibiotic resistance in human medicine, potentially linked to the use of antibiotics in food-producing animals. Regulatory bodies have mandated the reduction or elimination of antibiotics in commercial broiler production, prompting the adoption of specific gut health management programs. These programs range from conventional antibiotic use to raising chickens without antibiotics, necessitating a shift in strategies and dietary formulations.
The evolution of gut-friendly diets steer away from antibiotic reliance and towards multifaceted approaches. Enzymes, probiotics, prebiotics, phytogenic feed additives, and organic acids are among the alternatives investigated for their efficacy in preserving gut health. These ingredients complement dietary compositions by preventing undigested feed, maintaining a healthy microbiota, and fortifying antibacterial properties. Dietary fiber can also serve as a potent antibiotic replacer within poultry diets, exerting its impact on gut health through diverse avenues.
By fostering a balanced gut microbiome, fiber acts as a natural regulator, mitigating the proliferation of harmful bacteria while promoting the growth of beneficial microbes. This modulation aids in fortifying the intestinal barrier, enhancing nutrient absorption, and boosting the avian immune system. Moreover, the fermentation of fiber yields beneficial metabolites like SCFAs, which contribute significantly to gut health by reducing inflammation and maintaining a healthy microbial ecosystem. As an antibiotic alternative, fiber not only supports poultry health but also helps combat antimicrobial resistance while sustaining optimal gut function and overall well-being.
Impact of dietary fiber on nutrient usage and ammonia release
The impact of a fibrous diet on nutrient utilization and ammonia emission is significant. When dietary protein and amino acids aren’t fully digested by the host, gut microbes ferment them. Roughly half of these nitrogen sources are converted to uric acid and ammonia in the gut, leading to reduced nourishment and increased toxicity for the host. Subsequently, the uric acid transforms into ammonia in the litter through microbial activity, causing discomfort for birds and raising serious public health concerns.
While gut microbes typically prefer carbohydrates for energy, depletion of these substrates prompts certain groups of microbes to shift from carbohydrate breakdown to protein breakdown, generating odorous sulfur compounds, ammonia, amines, phenols, and indoles. Interestingly, when dietary fiber undergoes microbial fermentation, nitrogen sources like ammonia are used for bacterial protein synthesis, potentially decreasing ammonia emissions. In essence, fermentable fiber not only fuels microbial protein synthesis but also limits the fermentation of undigested protein into ammonia.
Impact of dietary fiber on gut microbiome
The poultry gut is home to many helpful bacteria that aid in digesting food and keeping the birds healthy. These bacteria are influenced by what the birds eat, and certain fibers in their diet can help good bacteria grow while keeping bad bacteria in check. As chickens grow, what they eat plays a big role in the types of bacteria that thrive in their gut. Some fibers in their food, called prebiotics, support the growth of beneficial bacteria, making the gut environment better for the chickens’ health. These prebiotics can also help remove harmful bacteria by making them bind to the food instead of sticking to the chickens’ intestines. Ingredients like certain fibers in the chickens’ diet can improve the growth of helpful bacteria and prevent digestive issues. However, there is still more to learn about how different fibers interact with the bacteria in the gut.
Impact of fiber fermentation products on gut health
When chickens digest fiber, their gut bacteria create useful substances like short-chain fatty acids. SCFAs like acetate, propionate, and butyrate are important as they are not just energy for chickens; they help the gut work right. Among SCFAs, butyrate is a star, keeping chicken intestines healthy and fighting bad bacteria. Butyrate helps the gut muscles and cells and even fights invaders like Salmonella. When chickens get butyrate, their intestines stay strong, especially when dealing with coccidiosis. It also lowers the gut’s pH, which stops bad bacteria from growing. Essentially, SCFAs from fiber not only give energy but also keep the chicken gut healthy. Probiotic bacteria like Lactobacillus can also boost butyrate production, helping digestion. Certain additives in chicken feed, like enzymes or inulin, can increase specific SCFAs, which can benefit chicken health.
Impact of fiber on the integrity of the gut lining
The fiber in a chicken’s diet can shape how their gut works and how well they absorb nutrients. Different types of fiber affect the lining of the gut differently. Some fibers, such as oligosaccharides of fructose, xylose, mannose, or galactose, can boost the size of finger-like projections called villi, which help with nutrient absorption. This can mean chickens grow better, enhancing nutrient absorption from the gut. These fibers can also help protect against harmful bacteria by strengthening the gut’s defenses. They do this by influencing proteins that make up the gut lining, which in turn can help prevent infections. These fibers also impact the gut’s immune system, promoting better defenses against diseases. They stimulate immune cells and help produce substances that fight off harmful pathogens like Salmonella. Additionally, fibers can reduce stress in chickens and improve their immune responses.
Examples of feed ingredients that bring fiber benefits to poultry gut health and performance
The prices of many grains and legumes used in poultry feed are rising because more people are using them for food and fuel. To manage this, poultry feed often includes alternative ingredients like wheat middlings, soy hulls, oil cakes, distillers dried grains and solubles (DDGS), and sugar beet pulp. However, these alternative ingredients have a lot of dietary fiber made up of non-starch polysaccharides (NSP), lignin, and other plant-based carbs that chickens cannot fully digest. This type of fiber in feed can hinder nutrient absorption by enclosing them within plant cell walls, impacting digesta viscosity, and interfering with mineral uptake. Although microbes in the gut use dietary fiber to create beneficial SCFAs through fermentation, the low digestibility of viscous NSP reduces the apparent metabolizable energy of the feed. This increased viscosity can disrupt the digestibility of other nutrients. Improving fiber digestibility through preprocessing and enzyme supplementation not only boosts its utilization but also enhances the availability of fermentable resources for gut microbes. These resources, varying from complex fragments to simple oligomers, could potentially act as prebiotics, supporting beneficial bacteria growth, immune system modulation, and overall gut health.
Distillers dried grains and solubles play a crucial role in poultry gut health through their fiber content. Fiber in DDGS, including soluble NSP, serves as a fermentable substrate for beneficial bacteria in the gut. This fermentation process produces short-chain fatty acids like butyrate, which is known for its positive impact on gut health. Butyrate supports the integrity of the intestinal lining, enhances nutrient absorption, and contributes to a balanced gut microbiota. By providing fermentable fiber, DDGS contributes to a healthier gastrointestinal environment in poultry, promoting better digestion and overall well-being.
Adding yeast cell walls rich in β-glucan to poultry diets has some great perks. It can boost Immunoglobulin A (IgA) secretion in the gut, stimulate both types of immunity (the kind that produces antibodies and the kind that involves cells), and might help the birds fight off coccidiosis better. There is also some good news about using DDGS — those contain a bunch of NSP and yeast β-glucan, which seem to crank up IgA and IgG levels and even turn on genes related to the immune system in broilers. In one study, mixing sugar beet pulp with rice hulls in the right amounts (about 3% of the feed) doubled antibody levels against Newcastle disease in broilers. And here’s an interesting thing: feeding chickens oligosaccharides seems to lower their stress by reducing heterophil counts. Stress can mess with a bird’s gut, immune system, and overall health, so it’s good to keep an eye on that. Bottom line: giving poultry diets with fermentable fiber could really perk up their gut health, boost their immune systems, and help them soak up nutrients better.
In the realm of poultry feeding, understanding the nuances of soluble versus viscous dietary fiber becomes crucial. While soluble fiber fosters microbial activity, the impact of viscous fiber on nutrient absorption efficiency cannot be overlooked. Balancing these dynamics remains challenging, requiring careful formulation and management strategies to optimize gut health without compromising nutrient utilization in poultry production.
References:
Bedford, M. R. and J. H. Apajalahti. 2022. The role of feed enzymes in maintaining poultry intestinal health. Journal of the Science of Food and Agriculture. 102: 1759–1770. (Link to the article).
Jha, R., and P. Mishra. 2021. Dietary fiber in poultry nutrition and their effects on nutrient utilization, performance, gut health, and on the environment: a review. Journal of Animal Science and Biotechnology. 12, 51. (Link to the article).
Hodgins, L. B. and E. G. Kiarie. 2021. Mandated restrictions on the use of medically important antibiotics in broiler chicken production in Canada: implications, emerging challenges, and opportunities for bolstering gastrointestinal function and health — a review. Canadian Journal of Animal Science. 101(4): 602-629. (Link to the article)
Min, Y.N.; Li, L.L.; Liu, S.K.; Zhang, J.; Gao, Y.P.; Liu, F.Z. 2015. Effects of dietary distillers dried grains with solubles (DDGS) on growth performance, oxidative stress, and immune function in broiler chickens. Journal of Applied Poultry Research. 24, 23–29. (Link to the article)
Sadeghi, A.; Toghyani, M.; Gheisari, A. 2015. Effect of various fiber types and choice feeding of fiber on performance, gut development, humoral immunity, and fiber preference in broiler chicks. Poultry Science. 94, 2734–2743. (Link to the article)
Singh AK, Kim WK. 2021. Effects of Dietary Fiber on Nutrients Utilization and Gut Health of Poultry: A Review of Challenges and Opportunities. Animals (Basel). 11(1):181. (Link to the article)
