chadm

Hi everybody, My dog sandy is a sheppard whippet mix about 50 lbs. I got her from the local shelter and she is now about 9 years old but looks younger ( sound familiar) she is going to kill herself I am afraid, she can accellerate from 0 to 40 mph in about 3 seconds and when she see's a squirrel or rabbit she has no concern or awareness what is between her and that small animal broken rocks, branches, a cliff whatever she goes over or under it while emitting a shrill high pitched bark. I suspect she has already injured her back. I hate to keep her leashed does any body have any suggestions?