Let me get this straight - TC 's hubby is Lucky_P?? Good to know!
I had typed a long response to JMJ's comment, but realized there were more comments. Lucky described that PERFECTLY!! I have had several articles about the subject in my newsletter.
Not saying 3 yr olds don't make "smarter" momma cows - not saying they do either. I have calved 2 yr olds for nearly 50 years, and mothering has been nearly a 0 factor. Many, many years ago we had one heifer that refused to take care of her calf. Hubby almost got the gun. He was livid. Got the dog instead. Funny how impending danger to the offspring will "kick-in" the instincts. Being 100% AI, I should have trouble with the 2yr olds getting rebred, but we don't. They may fall off 3 weeks, but I try to get them to calve the first week of our 60 day calving season, so they still have plenty of time for a repeat.
Time is money. I don't like to waste 6 months. And, I don't believe in "wasting" that first calf. Out of 6 in my show string - two were out of 2 yr olds. One Jan calf won several Supremes this season. I do not pick out a super CE "heifer bull". I don't breed to super hard calvers, but I expect my heifers to work for me. Don't know when the last heifer needed assistance for a normal presentation calf, but I do know it has not been since some time prior to Jan 2013, since nephew has been here.
Back to OP - wait 10-14 days and Lutalyse. Cheap and safe.