To maximize the absorption of nutrients from food, the mucosa has to have a large surface area. This is achieved through the lining of the IECs being arranged into folds of finger-like projections called villi. Damage to or alterations in this structure can lead to a decrease in the area of the gut available to absorb nutrients. Factors such as diet and disease play an important role in the development and maintenance of villi structure.3
In addition to the physiological protection properties of the gut, the IECs are able to detect and react to harmful microorganisms. The gut is actually the largest immune organ in the body and can mount an appropriate immune response very quickly.2 This early response is known as ‘innate’ immunity. When the IECs come into contact with a harmful substance, they initiate the production of molecules and chemicals. Some of these have anti-microbial properties and target the invader directly. Other chemicals recruit more immune cells for an even stronger, prolonged response. This is termed ‘adaptive’ immunity as the response is modified depending on the specific threat.
Microbes and the gut
Another key factor at play in the preservation of gut health is its natural microbial flora composition. This includes bacteria, fungi, and protozoa although bacteria predominate.4 The development of this community usually begins at birth and is influenced by bacteria picked up from the environment, the feed and farm personnel. There are billions of microbes present in the gut, the majority of which are non-harmful. In fact, presence of beneficial ‘commensal’ bacteria is essential for maintaining good gut function.
The interactions of the gut’s microbial flora are extremely complex and ways in which it is thought to contribute to gut health are numerous. These include synthesis of vitamins, improvement of food absorption and inhibition of detrimental pathogenic bacteria. There are also positive effects on gut motility.
One mechanism by which beneficial bacteria provide protection against pathogenic organisms is competition for colonization sites and key nutrients.2 Beneficial microbes also have a role in stimulating the immune system and maintaining the health of the IECs, which contributes to the animal’s defense system. They play a key role in signaling for healthy gut development, having an impact on factors such as villi length and structure. All of these mechanisms are not mutually exclusive and are likely to occur in combination to help maintain a healthy gut. 5
The diets of many production animals contain non-digestible portions, often of fibrous origin. It is the beneficial microbes which are able to break down this non-digestible fiber, making the energy available to the host. Product of this process are short chain fatty acids (SCFAs) which can be used for energy by the gut and other organs in the body.6 Without this microbial metabolism, the potential of certain types of dietary components would remain unused.
There are a number of factors which affect the integrity and function of the intestinal mucosal barrier and the microbial composition in the gut. Diet plays a large role, with certain nutritional components favoring the production of particular bacterial populations. The physical texture and quality of the feed will also have an impact.
The overall health of the animal as well as environmental exposure to certain pathogens can cause a shift in the bacterial population. The use of antibiotics can also upset the balance of bacterial populations in the gut. This is why it is preferable to target specific bacteria using ‘narrow’ rather than ‘broad’ spectrum antibiotics when such treatment is necessary.
As immune defense is so important in maintaining gut health, stressful periods, or other factors which cause immunosuppression, will place animals at higher risk of intestinal compromise.
Consequences at farm level
So, it’s clear that poor gut health can arise due a series of interacting factors but what does this mean in practical terms? If the gut’s structure, microbiota or immune function does not fully develop or is compromised, productivity will be negatively affected. Microbiota composition plays an important role in effective food digestion and absorption, so perhaps it’s not surprising that there’s a correlation between microbiota composition and FCR.7,8
A poor or inappropriate immune response can also have a negative impact on FCR as a result of diverting energy and nutrients away from production.7 This means that focusing on maintaining a healthy microbial balance and intestinal immune system will have direct benefits for productivity and profits.
Gut structure and morphology also has an impact – the greater surface area available to absorb nutrients, the more potential there is for improved growth. Another important consequence of poor intestinal integrity is an increased susceptibility to diseases, such as coccidiosis
Improving intestinal health
Diet, environmental management, animal husbandry and biosecurity are all important in regulating gut health. Manipulation of nutrition and supplementation in particular can have profound effects in optimizing gut health. The opportunities presented by SCFAs in this regard are becoming more widely recognized, having an effect on a number of the vital structural and functional aspects of gut health.
Of the SCFAs, butyrate is of primary importance when it comes to gut health with tributyrins being one of the most effective forms of this product available. Supplementation with butyrate across a variety of species including poultry, pigs and ruminants, has been shown to have many functions over and above providing an additional source of energy.9 Butyrate has been shown to improve nutrient digestibility, increase mineral absorption, optimize the profile of intestinal microbiota, down regulate bacterial virulence and support tissue development and repair.9,10 Beneficial effects on the integrity of the epithelial cells and the gut’s defense systems have also been demonstrated. SCFAs like butyrate can increase mucosal surface area and create a larger absorptive capacity. It’s likely that all of these factors combine to result in improvements in feed conversion rates and weight gain which are seen with butyrate supplementation.9, 10
Gut health – the key ingredient
Good gut health is vital for getting the best growth and FCR out of any food producing animal. The gut is a highly complex organ and maintaining its health involves optimizing many aspects of management, with a focus on diet as a key influencer of gut structure and function. As food producing industries face increasing challenges, tools that exert positive effects on gut health are becoming even more important for producers looking to achieve a competitive advantage.
1. Choct, M. (2009). Managing gut health through nutrition. British poultry science, 50(1), 9-15.
2. Kraehenbuhl, JP and Neutra, MR. 1992. Molecular and cellular basis of immune protection of mucosal surfaces. Physiology Reviews, 72: 853–879.
3. Uni, Z. E. H. A. V. A., Ganot, S. A. H. A. R., & Sklan, D. A. V. I. D. (1998). Posthatch development of mucosal function in the broiler small intestine. Poultry Science, 77(1), 75-82.
4. Guarner, Francisco, and Juan-R. Malagelada. Gut flora in health and disease. The Lancet 361.9356 (2003): 512-519.
5. Yegani, M., and D. R. Korver. "Factors affecting intestinal health in poultry." Poultry science 87.10 (2008): 2052-2063.
6. Patterson, J. A., & Burkholder, K. M. (2003). Application of prebiotics and probiotics in poultry production. Poultry science, 82(4), 627-631.
7. Apajalahti J.,Rinttilä T, Kettunen A, Does the composition of intestinal microbiota determine or reflect feed conversion efficiency? 23rd Annual Australian Poultry Science Symposium, Sydney, New South Wales, 19th -22nd February 2012
8. Gabriel, I., M. Lessire, S. Mallet, and J. F. Guillot. 2006. Microflora of the digestive tract: Critical factors and consequences for poultry. World’s Poult. Sci. J. 62:499–511.
9. Besten G., Eunen K., Groen A., Venema K., Rejngoud D., Bakker B., (2013), The role of short-chain fatty acids in the interplay between diet, gut microbiota and host energy metabolism, The Journal of Lipid Research R036012 http://www.jlr.org/content/early/2013/07/02/jlr.R036012.full.pdf+html
10. Gilloteau P., Martin L., Eeckhaut V., Ducatelle R., Zabielski R., Van Immerseel F. (2010) From the gut to the peripheral tissue: the multiple effects of butyrate. Nutrition Research Reviews, 23: 366-384