The present invention relates to the use in animal feed of a xylanase having a percentage of identity to a Paenibacillus xylanase having the sequence of amino acids 1-184 of SEQ ID NO: 4 of at least 82.7%, as well as to feed additives and feed compositions comprising such xylanase. These xylanases are significantly better than known animal feed xylanases to solubilize and also degrade insoluble fibre polysaccharides (Non-Starch Polysaccharides, abbreviated NSP), such as arabinoxylan polysaccharides.