I went a bought one of those starter pistols, like they use for races, and each and every time my heelers or Aussie acted up....I fire it.    They would  stop dead in their tracks.

Here the BIG  problem is chasing deer and that will lead to who knows where...found one dog 5 miles away once.   The starter pistol is small enough to keep in your pocket...shoots blanks...but for me it's been the best 'dog whistle' I've used and I've trained a lot of these dogs. 

Hand one dog who would go after the testicles on the bulls!   Of course the bulls helped me out on this problem...but the pistol worked wonders.

These dogs are strong willed and you need to prove to them that YOU are the alpha dog .  Hope this helps out.