If they are going to respond , they will do it in 24- 48 hrs. Keep in mind that all will not respond. You can give the Lutalyse and breed what comes in heat , wait about 7 days after the first shot and give a shot to those that didnt come into heat and you will get most of the rest on the 2nd go around. Use 5cc per head .I would breed on visual heat , not timed breeding .