Now that Karen mentions it, I do remember spraying the cows with flyspray when we brought them in the barn for milking at night - I suspect that the flyspray we used in the sprayers we used like the ones below would not be allowed now. Back in the 1940s, I think we were still using flyspray with DDT in it.
(http://www.vtgrandpa.com/photos/albums/forum_photos/flysprayer_1940.jpg)