cat heat cycle

Question
A cat that was left at my house, seems to be in heat. The neighbor cat is trying to breed her. I want to know how long this cycle  (days) will last. I have her pined up so he can't get to her.

Answer
She will be in heat until she is bred. If you want the cycle to stop, take her in the vets and get her spayed tomorrow. That will end it once and for all.
Otherwise you will have kittens unless she is inside. They can breed right through a fence and pen walls.