Every female is different. Some ovulate early like day 9 and then I had a female that ovulated on day 18. I count from the first sight of blood. If you really want to breed your female I suggest you call your vet and ask to have a progestrone test done. This tells you exactly when she's 'ready'. Females can be in heat for 2-4 wks, out of that time she is only fertile for 48hrs.
I think it's great you are asking a question, however purposely breeding for pets is not neccessary, there are PLENTY of Yorkies in Rescue that would make loving pets and need homes. You may want to ask your self if the risks and costs involved with having puppies is worth providing pets for friends and families.
Happy Holidays!
Irene |