A new proof for the mechanism of action of in-feed resin acids was presented at the 7th International Conference on Poultry Intestinal Health (ICPIH2022). Dr. Hannele Kettunen presented a study conducted by Hankkija Finnish Feed Innovations, Alimetrics Ltd and GeneVia Ltd, which indicated that the positive intestinal effects of resin acids are related to their effects on gastrointestinal mucosa.

We have previously shown in multiple experiments that dietary resin acids improve the production performance and intestinal condition of broiler chickens and turkeys by improving the balance of intestinal microbiota and reducing the inflammation-associated breakdown of gut tissue.  

During inflammation, the expression of specific intestinal collagen-degrading enzymes, matrix metalloproteinases (MMPs), is upregulated. These enzymes degrade both the collagen layers of the villous surface of gut, and also break down tight junction proteins. These changes lead to gut barrier loss and intestinal leakage, which then leads to inflammatory processes in intestinal tissue. Hankkija Oy has shown that when broiler chickens have resin acids in the diet, the expression of inflammation-associated MMPs is inhibited, and inflammatory changes in gut mucosa are reduced.  

To study this phenomenon further, we conducted a new broiler trial at the poultry research facility of Alimetrics Ltd. The specific aim of the trial was to identify genes and genetic pathways of ileal mucosa which are affected by dietary resin acid concentrate (RAC) which contains 37.2% resin acids.     

Male Ross 308 hatchlings were randomized into 20 pens, 14 birds/pen, and two diet groups (10 pens/group): 1) control wheat-soy -based diet, and 2) the same diet amended with 175 g/ton of RAC.   Bird performance and feed intake were measured for the starter (days 1–21) and grower (days 21–35) periods and over the whole 35-day study. The results of this performance part of the trial are presented in Table 1. Compared to control birds, birds in the RAC group were 8.6% heavier on day 21, and 5.7% heavier on day 35 (p<0.05 for both). Moreover, they had an improved feed conversion ratio for days 1–21 (–6 points; p<0.05).



FCR, mortality corrected



















Table 1. Performance results

To study the effect of dietary resin acids on intestinal gene expression, two birds/pen were sampled for gut mucosal tissue on day 21. Total RNA was extracted from 6 control group samples and 6 RAC-group samples and sequenced using an Illumina instrument. The sequencing data were analysed with several statistical tools to illustrate the effects of resin acid treatment: principal component analysis (PCA), differential expression gene (DEG analysis, and Gene set enrichment analysis (GSEA), using R software.  The DEG analysis revealed 27 genes with different expression between the treatments (p<0.05). The GSEA analysis which shows suppressed and activated biological processes, recognized 10 activated and 10 suppressed processes in RAC-group, compared to Сontrol group (Figure 1). One of the significantly suppressed processes was ‘Extracellular matrix organization’, which includes the MMP2 protein coding gene. Specific pathways related to inflammation were not altered by the dietary RAC amendment.

Figure 1. The gene sequencing results

In conclusion, the present study confirmed earlier findings on the performance-enhancing effects of RAC. Both the birds’ weight gain and FCR were improved by the resin acid amendment.

The study indicated that RAC affects biological processes related to extracellular matrix, including expression of MMP2, thus supporting previous research which has indicated less MMP activity in ileal mucosa with resin acids-fed birds.

Hankkija FFI continues to study the mechanism of action of resin acids in collaboration with Prof. Filip Van Immerseel’s research group at the University of Ghent, Belgium.


Kettunen, H., Simao, F., Vienola, K., Vartiainen, S., Apajalahti, J., and Vuorenmaa, J. 2022. Effects of in-feed resin acid concentrate on growth performance and ileal gene expression of broiler chickens. Abstract id-87 at: 7th International Conference on Poultry Intestinal Health (ICPIH2022), Cartagena De Indias, Colombia, 30 March – 1 April, 2022. (Poster)