The Wealth of Nations by Part 1 Chapter 11 Page 232

Their cattle are allowed to wander through the woods and other uncultivated grounds, where they are half-starved; having long ago extirpated almost all the annual grasses by cropping them too early in the spring, before they had time to form their flowers, or to shed their seeds. The annual grasses were, it seems, the best natural grasses in that part of North America; and when the Europeans first settled there, they used to grow very thick, and to rise three or four feet high. A piece of ground which, when he wrote, could not maintain one cow, would in former times, he was assured, have maintained four, each of which would have given four times the quantity of milk which that one was capable of giving. The poorness of the pasture had, in his opinion, occasioned the degradation of their cattle, which degenerated sensibly from one generation to another.