When was the last time he threw a litter? I had a conversation with 3 different reproduction vets. All say that with older males you have to clean them out. So say you know your bitch is gonna be ready on the 15th. Clean the male out on the 5th and 10th. This will remove the dead sperm and allow him to make new sperm. So you can stick her on the 15th and the 17th and start praying