Who Let The Dogs Out

"If you have a good dog, trust your dog."

When in a day care situation or a situation with unfamiliar dogs how do you know when to get involved? I know you've said no blood no foul, but obviously you don't know you have a problem you need to intervien with until there is blood? How often do you see small puncture holes (I'm talking the through the skin punctures with no extra tearing or deeper) in day care? Do you ever have real dog fights?

 By my definition, a spat is is over in three seconds. Most dogs DO NOT attempt to maim or kill. That is not normal. Each dog just wants his way.
Want the ball. Want to be left alone. Want to hump you.
We have a lovely chow x husky mix female in our day care. When a new dog comes up to her for the first time, she shows her teeth and snaps them at the new comer. She does not like rough play. We know that she is setting the ground rules with her new friend. We trust Mandy to do that.
Day care dogs are not unfamiliar to us.
In three seconds you should be redirecting your group and assessing the situation.
The goal with a group of dogs is to keep them happily involved in play. When you see them getting stiff legged and uncomfortable with each other, redirect. We must be leaders in the park. 
We panic at a grumble, then over correct a dog from a place of fear. 
The point is to direct or lead the dogs, but to not panic at a spat. 
Shaker's confidence has been shaken by his run in with Stoney. He is more reactive. Do I trust him? Yes, he is a good dog. Will I break it up if he grumbles at another dog? No. I will redirect his attention and praise him when he calms down again. He needs to learn to trust the other dog will respond appropriately to his signals. When he signalled submission, Stoney continued to attack him. Now, he is more reactive with some dogs he doesn't know.
I need to help him rebuild his confidence. Dr. Temple Grandin teaches us what a strong emotion fear is for animals. I need to give him some space to deal with his fear. When he does, I let him know how wonderful he is. My praise calms him right  down. His confidence will return in no time. 
If a dog is afraid and we correct him, that further erodes confidence. The goal is to have enough of a realtionship with your dogs that you can redirect instead of having to correct.
In the six years that I did the day care here, I never had a spat let alone a fight. I read the signals and stay ahead of the behavior. 
Until you get to that point, learning to trust a good dog reduces trouble. Klondyke, a husky in our day care since puppyhood will correct a misbehaving newbie. They listen to him; he speaks the language. The new dogs are the ones to watch, we get a feel for how they handle the comptetion of the chase for a ball or the attention of the handler. 
We evaluate the dogs before accepting them into day care. Reactive dogs are not accepted. 
Most wounds are from two dogs going for the same ball complete accidents. A spat can result in a puncture. Some dogs are reactive when going through gates or doors. They require special handling. We keep records of which dogs are involved in incidents. I don't want a dogs in day care that can't control their teeth.
Don't wait for blood! They have three seconds to solve it on their own after that you have a dog fight. We separate dog fights.
I had a couple of Bullmastiff sisters that would fight. It looked scarey to see these two big girls. Each wanted to win, but they never had a mark; that's no blood, no foul. Did we separate them? You bet.
Here is my rule: if you can't stay ahead of the dog's behavior to prevent a spat; give them the three seconds to settle it. Take that deep breath, then do what you need to do. 
These are skills that take time to develop. I see more wounds with overreactive handlers who try to micro manage the dogs.
We keep track of who is in charge when an incident occurs.
Puncture wounds here are infrequent enough that they still upset me greatly when they happen. I get all on the war path with my staff because we are the humans in charge. 
 Does this clarify? Does it bring up any other questions?