The utilisation of in-feed resin acids as an alternative to antimicrobial growth promoters

21 June 20245 min reading

Shah Hasan, PhD
Technical Manager
AB Vista

Resin acids sourced from coniferous trees represent phytochemicals with historical applications in Asian and Scandinavian traditional human medicine, dating back to ancient times. Recent research on the in-feed applications of resin acids reveals the unique mode of action of this ingredient.

For more than half a century, antimicrobial growth promoters (AGPs) have played a decisive role in livestock production. In recent years, concerns have been raised regarding the overuse of antibiotics, leading to regulations restricting their use as AGPs, with more research on antibiotic alternatives published. Yet, surprisingly, there is still a lack of knowledge about the exact mechanism of action of AGPs. 

Research has centred around two main hypotheses. The first, and most researched, is on the effect of antibiotics on the composition of microbiota populating the intestine. The second looks at the direct effect of antibiotics on host cells, especially those involved in the inflammatory response, which has gained scholars’ attention (Niewold 2007).

It is most likely that both play a significant role in delivering the efficacy of AGPs; the effects might be interdependent. If we focus on intestinal integrity affected by inflammation, we can support it either indirectly, by stimulating the microbes that provide metabolites utilised by epithelial cells, or directly, by reducing the negative impact of inflammation.


Intestinal health is critically important for the digestion and absorption of nutrients and is thus a key factor in determining animal performance. Intestinal health issues are very common in high-performing animal lines due to the high feed intake, which puts pressure on the digestive system. Excess nutrients that are not digested and absorbed in the small intestine may trigger dysbiosis (i.e., a non-beneficial shift in the microbiota composition in the intestinal tract).

Fostering a thriving community of beneficial microbiota in the lower part of the intestine (hind gut) plays a crucial role in promoting overall animal health. The microbes in the hind gut need nondigestible fibre – there should not be any digestible nutrients in the hindgut, but instead non-starch polysaccharides (NSP). 

NSP can be broken down to lactate and acetate – intermediate metabolites – which are then further converted to short chain fatty acids (SCFA), propionate and butyrate. These SCFA are an energy source for the host epithelium. When small intestinal digestion and nutrient absorption are interfered with due to tight junction leakage, inflammation and dysbiosis (also known as triggers of the triad) or any other reason, this results in an excessive amount of protein in the hind gut. In turn, this allows pathogenic bacteria like Protobacteria (Desulfovibrio) and Enterobacteriaceae (Salmonella) to grow. 

Aside from nutritional stressors, it has been established that any environmental stressor (e.g., heat) which induces dysfunction of the gut barrier will trigger inflammation. Damage to the gut barrier allows leakage of potentially harmful compounds and microorganisms – bacterial translocation, an example of which is Enterococcus cecorum – from the intestinal lumen into the portal circulation, and from there directly to the other organs. Even minor deficiencies in intestinal health may have deleterious effects on the general health and performance of production animals. 


It is well established that even in perfectly healthy animals there is always a certain level of ‘physiological inflammation’ in the gastrointestinal (GI) tract. Pathologies caused by the aforementioned stressors may result in an excessive local immune response against luminal antigens. This, in turn, promotes a pathological process that leads to various degrees of intestinal damage.

Matrix metalloproteinases (MMPs) are a family of neutral proteases with the ability to degrade all components of the extracellular matrix. In normal physiological conditions, MMPs are produced at a very low level, generally in the latent form, and are involved in the regular tissue turnover. Their function is regulated by tissue inhibitors of metalloproteinases (TIMPs). However, in inflamed tissue, MMPs are produced in excess and/or the activity of TIMPs is not sufficient to block MMPs. This process can be a major contributor to mucosal degradation, leading to diseases such as necrotic enteritis – and thus, to significant financial losses.

Resin acids from coniferous trees have been found to inhibit the degrading activity of MMPs (MMP2, MMP7, MP9) in the extracellular matrix. The most profound effect on MMP activity through the supplementation of resin acids has been observed in the ileum, resulting in a reduction of both collagen type I and collagen type IV degrading activity. 

Both collagen subtypes are important for the structural integrity of the intestinal wall: collagen type I is a major supportive component of the extracellular matrix; collagen type IV is an integral component of the basement membrane supporting the epithelial cells.

However, MMP7 is more significantly linked to injured epithelium and seems not to be involved in regular epithelial renewal. It disrupts epithelial barrier integrity by degrading intercellular junction molecules, such as cadherins and occludins. Coniferous resin acids are proven to reduce the collagenolytic activity of both latent and active forms of MMP7.

The utilisation of resin acids in animal feed – commercially available as Progres® – marks an innovative, substantiated concept from AB Vista. Notably, resin acids sourced from coniferous trees represent phytochemicals with historical applications in Asian and Scandinavian traditional human medicine, dating back to ancient times. Resin-based products have historically been employed for diverse therapeutic purposes, including the treatment of wounds, sores, pressure ulcers, and a wide range of skin-related issues. The integration of this time-honoured knowledge into contemporary animal feed practices underscores the potential width of applications for natural resin acids beyond the original contexts.

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