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?

As stated below on the minecraft wiki about breeding. Breeding has a 5 minute cooldown before they can be bred again.

Each animal which is fed its food will enter "love mode", preparing to breed with another animal in love mode. Animals in "love mode" emit hearts constantly and will path towards nearby animals of the same species that are also in love mode. The two animals will "kiss" for about two and a half seconds, and then a baby animal of the same species spawns either in between the parents or on the same blocks as the parent that was spawned first, which ends love mode for the parents. They will not be able to enter love mode again for 5 minutes. However, they can still be herded with the appropriate material, as can the baby. After the baby animal has spawned, it will follow its parents for 20 minutes before growing to full size.

A little math for a starting animal farm. Lets say you start off with 2 animals of the same species. You mate them and they generate a litte guy. The breeding gets on a 5 min cooldown and the cub starts his 20min journey to maturity. By the time your first cub reaches maturity and is also able to mate you have an additional 3 cubs maturing in 5 - 10 and 15 minutes. So after just 25 minutes you have a second pair of animals which you can breed. This wil double your breeding rate and nog have 2 cubs every 5 minutes. This takes 20 minutes to get effect as for the produced cubs take 20 minutes to reach maturity. In about 1 hour you have around 14 mature animals and around 10 cubs. At this time you have a proper farm going and you can go and do more interesting stuff.