concerned about young pup falling pregnant

Question
I have a 5 month old female pug x chi and a 3 year old Chihuahua,he is constantly trying to hump her,at what age should i separate them as I understand she is too young to have a litter yet.I am afraid to leave her with him

Answer
Hi. As soon as you notice signs of heat, swelling of the vulva or bleeding, get them apart. If you are wanting to have a litter, I would wait until she was as close to two as you can get her. Once the heat cycle is over, you can let them be together again, but you'll have to do this with each heat until you are wanting to breed her. Good luck!