The Wealth of Nations by Part 1 Chapter 11 Page 14

But the relative values of those two different species of food, bread and butcher’s meat, are very different in the different periods of agriculture. In its rude beginnings, the unimproved wilds, which then occupy the far greater part of the country, are all abandoned to cattle. There is more butcher’s meat than bread, and bread, therefore, is the food for which there is the greatest competition, and which consequently brings the greatest price. At Buenos Ayres, we are told by Ulloa, four reals, one-and-twenty pence halfpenny sterling, was, forty or fifty years ago, the ordinary price of an ox, chosen from a herd of two or three hundred. He says nothing of the price of bread, probably because he found nothing remarkable about it.

An ox there, he says, cost little more than the labour of catching him.