apparently ours do.....you can smell it in the hay. they have litter boxes and they use the sawdust pile, which is fine....but NOT the hay!! One male one female both fixed. The horses still seem to be eating it all up though......can they get sick from that?? We've had horses for years but the cats are new. We got tired of the critters and the cats are doing a good job keeping that under control. Any ideas???