We have a nice 10 year old cow that has calved every year, so 8 calves on the ground. We have not been able to stick her AI (we tried several years of AI), so we put embryos in her (we bought her as a 6 year old). I really want a heifer from her before she is too old, so the person we bought her from said to use two straws. He said that her uterus is big from so many calves. So we stuck two straws in her, one right after the other, and she is now 25 days post her last heat. I sure hope we stuck her! I know she sticks an embryo each time... so she is fertile.