I don't live near any Horse slaughter plants, but we're close to many bird farms that raise and slaughter and the smell is awful, but no worse than the smell of people spraying fields with fertilizer. My friend lives right next door to a slaughterhouse that does large livestock, cows, horses and some pigs. It was run very well in the past, there was no smell and they did most of their business in the early mornings, the rest of the day was processing so there was very little noise / commotion throughout the day. There was absolutely no smell, and no rise in horse theft. However when it fell into bad management things changed, there was always lots of commotion, distressed animals, smell, etc.