Heat cycles for different lines of Cur dogs.

I raise ybmc and I only use the females. So with that said have not noticed any of them not having a heat cycle. And they have 2 a year.They are used on cattle and hogs. Several years back I get a female to my cousin and she was the only dog on the yard. She had one heat and that was all she ever had. I think it had do with not being around other females. They are pack animals or at least that is what dogs started out to be. Im sure that withs mans getting in the middle of things, We have changed some things along these lines. But Im no expert by no means. There are people that are a lot smarter than me that may be able to answer your question.