I have 15 chickens 4 roos and 11 hens. As of a few months ago, around the time my sisters dog attacked my flock, my hens stopped laying. Now 4 hens are 6 years old, and 1 had a baby with her as of when this dog attacked, chick was killed, but they have all ben laying well until that insident. now my 3 other hens don't lay and the other 3 are to young. why did they stop?