SummaryKynurenic acid (KYNA) was found to be an antagonist of iontropic glutamate receptors and alpha7 nicotinic acetylcholine receptors. Furthermore, it was documented thatKYNAis an agonist ofG‐protein coupledGPR35 receptors which are mainly present in the gastrointestinal tract. It was also found thatKYNAis present in the gastrointestinal tract and that its concentration gradually increases along it. The origin ofKYNAin the gastrointestinal tract is not known. Both might be synthesized from tryptophan in it or absorbed from food and other dietary products. Therefore, the aim of the study was to investigate the concentration ofKYNAin animal feed. The results indicate that the highest concentration ofKYNAwas found in animal feeds intended for livestock. The lower amount ofKYNAwas detected in animal feeds for fish. Interestingly, the lowest amount ofKYNAwas found in dog and cat feeds. Furthermore, an analysis ofKYNAcontent in animal food ingredients was conducted. The concentration ofKYNAfound in one of the ingredients – rapeseed meal – was several times higher in comparison to animal feeds studied. The content ofKYNAin the remaining feed ingredients tested was significantly lower. This is the first report on the concentration ofKYNAin animal feeds. There is a need for further detailed analysis leading to establishing a set of guidelines for animal feeding.