In the first article in this series, we discussed the increasing demand for poultry meat due to both population growth and an increase in per capita consumption, and its related effect on the incidence of production diseases in poultry production systems. Last month, we investigated the interactions between the poultry gastrointestinal tract (GIT) and the animal’s immune function, and how feed additives may impact this. In this, the last article in the series, we will take a closer look at the interactions between the microbiome present in the gut and nutrition, and how feed additives may impact on this.
The microbiome and nutrition
The development of the GIT and nutrient absorption are complexly related. It is believed that a more robust GIT will make for a healthier chicken, which, in turn, digests and utilises nutrients more efficiently. This link between enzyme activities, gut weight and growth performance has been studied extensively. Dietary characteristics such as nutrient content, feed processing method, digestibility of nutrients and feeding method may all change the balance in the gut microbiome, especially in young animals such as broiler chicks.
In poultry it seems that volatile fatty acid (VFA) production of the gut microbiome can be manipulated by diet. In a study by Choct et al. (1996), they demonstrated that the addition of soluble non-starch polysaccharides (NSP) to a broiler diet drastically increased the production of VFA in the small intestine, which was easily reversed when an enzyme designed to aid in NSP digestion was added to the feed.
Maintaining optimal digestion
Undigested nutrients in the hindgut of poultry promote the proliferation of bacteria, fungi, protozoa, and even viruses, as there are more undigested nutrients available for their use. This proliferation causes disturbances in the gut microbiota, which can result in changes in the regulation of adaptative immune cells and cause changes in microbial metabolism that can cause some microorganisms to become harmful.
A reduction in the digestion of feed nutrients or an excess of undigested nutrients in the GIT may occur for many different reasons in poultry. It is important that poultry diets do not contain an excess of nutrients, and that appropriate digestibility is guaranteed and consistently maintained to better control microbes and the production diseases they can cause. One strategy to achieve this is phase-feeding of broilers, which increases the precision of feed formulation according to the broiler’s requirements. If phase-feeding is not done well or if the phases become too long, excess nutrients, especially protein and fat, are not well digested or absorbed in the GIT, promoting microbial proliferation in the caeca. These bacteria can go back to the ileum and jejunum through reverse peristalsis, causing dysbacteriosis and even disease due to the production of endo- and exotoxins.
Other strategies to aid the maintenance of optimal digestion are the manipulation of feed texture, supply of good-quality water, quality control of dietary fat type and level, and addition of exogenous enzymes.
Exogenous enzymes are an excellent tool to control bacterial proliferation in the GIT. Phytases, carbohydrase enzymes, and proteases are used extensively in the poultry industry to reduce feed cost and enhance poultry production. An added benefit of using enzymes is their positive impact on the poultry gut microbiome. Phytase enzymes break down phytate, while carbohydrase enzymes reduce the viscosity of digesta, both reducing the irritation to the gut lining that causes inflammation. Enzymes can also generate metabolites that promote microbial diversity, which will assist in maintaining gut microbiome balance and limit harmful bacteria proliferation.
As we reach the end of this three-part series, we can conclude that finding suitable solutions to reduce the incidence of production diseases in poultry production systems is a complex problem requiring a holistic view. Improving and maintaining a stable gut microbiome is a critical factor in dealing with the challenge. We have many tools at our disposal to take on this challenge, but it will be important to find the most cost-effective solution for each situation together with your nutritional advisers.