I think cows win this one, mainly because they're one of the biggest food sources in the world. In most places where cattle are raised for food, they outnumber the human population by a few thousand/few hundred thousand to each single human. Chickens and sheep probably aren't far behind...it's possible chickens outnumber cows as well.

*ADD* Wiki, yeah...there's accuracy for you. LOL But yeah, chickens well outnumber cattle. World-wide they beat out farm animals in numbers, cats probably beat out dogs but their numbers are much higher than most farm animals can even hit, of course said farm animals are yearly harvested by the millions for food while dogs and cats are put down in the thousands but breed like rats since people don't get them fixed or dealt with, so their population stays nice and stable and useless. Of course, why dogs added in to a question with the rest being food animals?

Check out world-wide statistics on these, not wiki.Wiki is random and has some facts, but anything with numbers of this sort is usually off by a lot, in this case it's off by about a billion or three+ each. Of course that doesn't make the numbers very much closer together. ^_~

No, cattle do not win this, by a LONG way ! Here are the estimates from Wikipedia...

Cattle - 1.3 billion

Chickens - 24 billion

Sheep - 1.3 billion (not so confident on the source, though)

Dogs - 400 million

So there are more than 18 times as many chickens as cattle.

I'll guess less than 7 billion dogs, even if you count wolves, but ten billion each of cows, sheep and chickens.

I read somewhere that the numbers of each of these animals actually outnumbers the number of people in the world. I'm not sure if that is true or not, but it wouldn't really surprise me. In any case I am just curious which of the above animals has the highest population number. If you can provide a source for your info please do. Thanks.