Resin acids of Progres® do not accumulate in edible parts of broiler chicken nor in milk of dairy cows

Dr. Hannele Kettunen, R&D Manager

Consumer safety is of outmost importance to all players of the food chain, Hankkija FFI included. Novel feed materials must not only be beneficial to the farm animals, but they also need to be absolutely safe to the consumers of animal products. Hankkija FFI’s Progres® is the only feed ingredient containing resin acids of coniferous trees, so we are responsible for guaranteeing the safety of the product both for farm animals and for human consumers.

To begin with, it is fair to note that although new in the nutrition of domestic animals, resin acids are consumed by some of the most important wild game animals of the northern hemisphere. Resin acids originate from rosin, which is the natural protection mechanisms of coniferous trees against pathogenic microbes or parasites. Resin acids are found both in the trunk and needles of coniferous trees, and thus consumed in the nature by moose, hare, capercaillie, which feed on needles and young branches of pine and spruce, and which have been hunted by humans since ancient times. In Progres®, resin acids are in the same chemical form as in the trees, so the likelihood of seeing problems with Progres® was very low. But better safe than sorry!

According to our new research, resin acids do not accumulate to edible parts of broiler chicken, nor in the milk of dairy cows. 

The study with broiler chickens was conducted by Alimetrics Ltd, Finland, and recently accepted for publication in Frontiers of Veterinary Sciences (Apajalahti et al., 2020). In the experiment, commercial-type wheat-soy diets were either fed as such (control treatment) or amended with Progres® at 750 and 3000 g/t. The diets were fed to Ross 308 broiler chickens from the day of hatch to the age of five weeks. Each treatment was replicated 11 times. On the final day of the study, samples were collected from jejunal tissue, breast muscle, abdominal fat, blood, liver, bile and digesta along the intestinal tract. 

The study showed that although 75% of the resin acids became absorbed from the intestine of broiler chicken, most of it was recycled to the intestine via liver and bile, and voided via feces. Some may have become mineralized or metabolized by intestinal microbes or host tissues.  

No resin acids were detected in the adipose tissue, and the levels in breast muscle and liver remained very low. A serving of broiler dish prepared from a broiler fed with Progres® at 3000 g/ton (a four-fold dose!) would contain a maximum of 100 µg of resin acids. That is one-thousandth of the dose shown to be harmless in rodents. This means that resin acids in broiler products pose no safety concerns to human consumers.

The Progres trial with dairy cows was conducted in collaboration with Natural Resources Institute Finland. In the experiment, 12 cows received Progres® 7 grams/head/day from three weeks prepartum to 10 weeks postpartum, and equally many cows ate the same diet without Progres®. Milk samples were drawn from cows at 3 and 6 weeks postpartum for resin acid analysis and for sensory analysis. The concentration of resin acids remained below the detection limit of 20  µg/kg in all samples. The sensory analysis revealed no differences between the treatments either. As in the broiler chicken diet, resin acids were found in faecal samples of cows. The trial results, including the resin acid concentration in milk samples, will be published in a scientific journal. 


In conclusion, resin acids of Progres® do not end into the animal based products, and thus pose no safety concerns to human consumers of animal products. 



Apajalahti J., Vienola K., Raatikainen, K., Kettunen, H., Vuorenmaa, J. 2020. Distribution, metabolism, and recovery of resin acids in the intestine and tissues of broiler chickens in a feeding trial with tall oil fatty acid-supplemented diet. Front. Vet. Sci. (accepted)  doi: 10.3389/fvets.2020.00437