Justin...Why is this? My guess is that you are using the Ultra sound to look for sperm plugs in the male so you rotate him faster (ie. As soon as new plugs form?)...just curious.
Never used one myself, but I think you check the girls, not the boys. Then, only put him in with the ladies when their follicles are at the right size to be the most receptive to him. That way he doesnt breed the same girl 10 times, since she only gets pregnant once.

Hope that made sense.