The Wealth of Nations by Part 2 Chapter 1 Page 6

That part of the capital of the farmer which is employed in the instruments of agriculture is a fixed, that which is employed in the wages and maintenance of his labouring servants, is a circulating capital. He makes a profit of the one by keeping it in his own possession, and of the other by parting with it. The price or value of his labouring cattle is a fixed capital in the same manner as that of the instruments of husbandry. Their maintenance is a circulating capital in the same manner as that of the labouring servants. The farmer makes his profit by keeping the labouring cattle, and by parting with their maintenance. Both the price and the maintenance of the cattle which are brought in and fattened, not for labour, but for sale, are a circulating capital.

The farmer makes his profit by parting with them.