“No foot, no horse” is an old saying among horsemen. The proverb reflects both the susceptibility of horse feet to injuries and the importance of healthy feet for horses. For poultry producers, the saying could go as “No gut, no poultry”. Efficient nutrient uptake and feed conversion are crucial for the economics of modern poultry production. Industry professionals know how easily gut functions are disturbed.

The intestinal epithelium is an extraordinary tissue. Consisting of only one layer of intestinal epithelial cells, it needs to absorb all the vital nutrients for the animal, and yet maintain an effective barrier against pathogens and unwanted diet-derived particles. 

Key contributor to the proper functioning of gut epithelium is collagen. This highly abundant protein gives strength to bones, tendons and all other connective tissues throughout the body. Intestinal epithelial cells are literally attached to the collagen-rich basal membrane (shown in red in Figure 1). The extracellular matrix under the intestinal epithelial cells is also enforced with collagen fibres.

Figure 1: Villus of broiler jejunum: intestinal epithelial cells (brown), collagen (red)


The balanced physiological state of the intestine or other tissues is referred to as homeostasis. During homeostasis, both the uptake of nutrients and gut barrier both function efficiently, and inflammatory processes are under control. Homeostasis allows maximal performance of farm animals.

The delicate balance of intestinal mucosa can be challenged by pathogenic bacteria, fungi, viruses, mycotoxins, heat stress, low-quality diet, or other stressors. Prolonged stress to gut epithelium leads to inflammatory processes, including increased production of specific enzymes which degrade collagen fibers: matrix metalloproteinases (MMPs).

Collagen degradation by MMPs damages gut epithelium and reduces surface area for nutrient uptake. Gut barrier function is also weakened, resulting in the entrance of bacteria and their cell wall structures: the proinflammatory, fever-inducing lipopolysaccharide, LPS.

The ultimate aim of the inflammatory response is to remove infected or damaged cells, and to allow regenerative processes and restoration of homeostasis. However, intestinal inflammation consumes a lot of energy and nutrients, and therefore leads to loss of animal performance.


The research group of professors Filip van Immerseel and Richard Ducatelle (Faculty of Veterinary Medicine of the University of Ghent, Belgium) demonstrated that inflammation-associated collagenolytic activity of MMPs of broiler gut is significantly suppressed by in-feed resin acids (Aguirre et al., 2019).

The most profound effect of resin acids was observed in the ileum, in which the degradation of collagen types I and IV were significantly reduced. Both collagen subtypes are needed for the mucosal integrity: collagen type I is found in extracellular matrix, whereas type IV collagen is a key component of basal membrane.

The study suggested that resin acids inhibit a specific type of collagenolytic MMPs, namely MMP7 aka matrilysin. In the healthy intestine, various MMPs are expressed, but the production of matrilysin is mainly linked to injured epithelium. By suppressing the activity of matrilysin, resin acids likely reduce negative impacts of inflammation to intestinal integrity.

According to the same study, dietary resin acids reduced the density in inflammation-associated T-lymphocytes in the duodenal tissue. Thus, the anti-inflammatory effects of resin acids took place in all the three main compartments of the small intestine: duodenum, jejunum and ileum.

In conclusion, the natural resin acid composition inhibited collagen breakdown and suppressed the numbers of inflammatory cells in the small intestine of broiler chicken, thus supporting mucosal integrity and homeostasis.

The natural resin acid composition tested in the above-described experiments originated from Nordic coniferous trees. The same resin acid composition is the active compound of Progres® of Hankkija Finnish Feed Innovations, the only rosin-based feed material in the international markets. Progres® has given consistent performance benefits to broiler chickens in institutional experiments, especially in trials, which have included an intentional challenge factor, like coccidiosis, necrotic enteritis, or heat stress challenge. The protection of gut epithelial structure and function likely explains the observed performance benefits by Progres®.


Aguirre M., Vuorenmaa J., Valkonen E., Kettunen H., Callens C., Haesebrouck F., Ducatelle R., Van Immerseel F., Goossens E. (2019) In‑feed resin acids reduce matrix metalloproteinase activity in the ileal mucosa of healthy broilers without inducing major effects on the gut microbiota. In: Veterinary Research 50:15.