First thing I thought when I read the title was... do not use the stall We are using fly predators here this year. They get spread around the yard and manure pile but we also put two spoon fulls in the back of each stall. So the bugs travel around the stall and eat fly eggs before they hatch. When the stalls get mucked out, some bugs get taken out but with a new batch of bugs every two weeks the stalls get replenished regularly. I find the best way to keep the urine smell down is to clean them very well with lots of new dry shavings daily.