
I know that with some breeds you don't sometimes get a tie, which is why the males are held in place for at least a minute to ensure that Sperm is transfered so to speak. During the tie it is usually Prostatic fluid that continues to be ejaculated in bursts. This helps fuel the sperm, as they have a long journey in the lo9ng canine reproductive tract.
Hopefully you may get a mating with a tie next time, which is more satisfactory, but not strictly necessary, as long as he has ejaculated, and remained in contact with the bitch for a reasonable time, at least a minute or two.