Out of 12 males, I have one that hasn't bred for me so far, 1 that breeds most of the time but took a year off, and the others breed reliably. I have never had a receptive female turn down a male that was interested in breeding, and vice versa. (If the male isn't interested, he won't breed with any of the girls--if the female isn't interested, she won't breed with any of the boys--so far. I test them out to be sure, when it happens, and I have never found an 'incompatibility' issue).