To ensure sustainable animal production, maintaining optimum gastrointestinal health and functionality is essential. A well-developed, balanced and diverse microbiome is the by far the best protection to enhance intestinal health and improve production, providing the best insurance for a good performance. Early 2017 certain medications in the USA will be regulated as of how they are dispensed for chickens. The implementation of the Veterinary Feed Directive (VFD) will put a stop to over-the-counter sales of many of the antibiotics used for poultry and other livestock. Use of the VFD drug will be permitted only under the professional supervision of a licensed veterinarian. This reduction in antibiotic use is creating a void that must be filled to ensure maintaining production levels.
Currently commercial birds are fed diets containing different functional feed additives at low concentrations that trigger responses beyond their nutritional value. Two groups of compounds are particularly promising: Organic Acids (i.e. butyrate) and Phytogenics (botanicals). Most recently, exploring ways to optimize the efficacy of these two classes of functional feed additives has gained more attention at scientific community as well as the production side at the field.
Butyrate: where to deliver in the GIT
Sodium butyrate is a salt of the short-chain fatty acid butyric acid, which is the end product of fermentation of carbohydrates by anaerobic bacteria in the hindgut. It is a molecule that is well known for its ability to elicit many effects at the cellular or microbiological level in several tissues. The fatty acid is considered the most important energy source for intestinal cells and has multiple beneficial effects on vital intestinal functions.
Research and practical field experience confirm that butyrate alone or in combination with other dietary strategies reduces the incidence of necrotic enteritis. Several different cell types and bacteria that can be found along the entire gastrointestinal tract (GIT) are responsive to butyrate. Which part of this wide range of butyrate-dependent effects will be triggered, will therefore depend heavily on the enteric location where butyrate is delivered after oral ingestion. Butyrate, when fed unprotected, will be easily absorbed and metabolized in the frontal part of the GIT, the stomach.
Feed additive companies produce butyrate in a protected form to prevent gastric absorption and allow more absorption at the distal GIT, with positive results noted as animals benefit from butyrate delivered more directly to the intestinal mucosa. Coated butyrate is typically composed of beads containing butyrate that are embedded in a protective matrix of vegetable fat. For products with a higher fat content <50%, a significantly large part of the butyrate content might only be released as lipase is secreted in the duodenum, breaking down the protective lipid matrix, thus gradually releasing butyrate throughout the intestinal tract, which is often referred to as “target release” or “slow release”.
Through in vitro and in vivo testing, it has been shown that these molecules, as short-chain triglycerides, will not be absorbed in the stomach, but that the bonds on the outside end of glycerol will be cleaved off by pancreatic lipase, thereby releasing butyrate in the proximal part of the small intestine. Already in the small intestine, butyrate supports villi development, gut morphology and function.
Further on in the digestive tract, butyrate as an energy source for the colonic cells, it is a major precursor for lipid synthesis, used for incorporation into the cell membranes. By supporting the cell membrane structure, butyrate contributes to the maintenance of barrier and transporter functions in the gut. It is also evident by research findings how important of a role butyrate plays in the intestinal wound healing by its positive effect on tight junctions and gut integrity.
Botanical Products: How to Look for Effect on Microbial Activity
Botanical feed additives that are used in modern poultry production often consists of a mix of several components, specifically dried herbs, plant extracts or essential oils, that have been described to have favorable effects on digestion, blood pressure, anti-inflammation and hepatic protection. It is therefore a challenge to develop a botanical feed additive mixture with ingredients triggering several physiological responses, with the objective of supporting animal health and performance as much as possible. So, a more reliable approach is to select feed additive ingredients based on botanical components effects at lower concentrations, which are likely to be able to control bacterial activity thus improving gut health.
One of the potential mechanisms of botanical feed additives is their effect on quorum sensing (QS). Bacteria continuously secrete QS signals, which allows them to synchronize their behavior. More specifically, when the number (the quorum) of a certain bacterial species or group in an environment increases, so will the concentration of their secreted QS signals If a specific threshold of these molecules is reached, it will activate QS-dependent signaling pathways inside the bacteria, resulting in biochemical responses that are often associated with pathogenicity, such as the production of toxins.
As a consequence, compounds able to disrupt QS are being increasingly investigated in human medical research as potential alternatives to antibiotics due to their efficacy at low concentrations and the low chance of bacteria developing resistance against these non-lethal molecules. But QS has also been implicated to be of importance for veterinary and zoonotic pathogens, including Clostridium perfringens, Yersinia pseudotuberculosis, Campylobacter jejuni and Salmonella enterica subspecies enterica.
Gut health is essential for health and performance of production animals. Many feed additives, including butyrate and botanical products, have been commercialized to support intestinal development and function. Even when producers feed “perfectly” balanced diets, feed additives nowadays can offer essential and reliable support to maintain a healthy gut.