The present invention relates to a feed supplement which comprises a resin acid based composition comprising over 10% (w/w) resin acids for use in the prevention of growth of harmful bacteria in the animal digestive tract, in the prevention of intestinal disorders, in the modulation of microbial population of the animal digestive tract, in enhancing rumen fermentation, lowering rumen methane production and/or in binding toxins. The invention further relates to a use of the feed supplement and a feed composition comprising the feed supplement.