I'm personally not a big fan of in/linebreeding unless you have a lot of experience, the top half dozen bulls of a breed, and the eye/willingness/ability to cull mercilessly. Heifers should be bred at around 15 months to calf as two year olds. Some breeds don't reach puberty at that age, typically Brahman and some of the continental breeds. Many of those breeds are held to calf at three years old, if only to keep them in the same calving cycle as everything else. That way you don't end up calving all year long or in a time frame that doesn't work under your managment.
> If I was to keep the calves them
> being heifers from my three cows.
> Would it hurt to breed them with
> the same bull that fathered them?
> Or if one of the cows have a bull
> would it hurt to interbreed with
> him? Also how long should one wait
> years to breed heifers?