How often can animals breed?

After I've bred two animals, there is a time frame where they wont accept wheat/seeds/carrots, in order to breed again. However I've only got a couple of animals at this stage, and I would like to maximise the efficiency (i.e, minimise the time) in which I get to a relatively large flock/herd.

So, how long do I have to wait before trying to breed them again?