why we milk the cow in winter

In the darkest, coldest months, when the cow is only putting a few pounds in the bucket and the low tunnels are full of spinach that freezes despite two layers of cover, we go on milking and sweeping the snow off the tunnels, not for six pounds of milk and some mushy leaves, but for the promise, dim and watery, that when spring comes (will it ever come?), and the sun shines again, the cow's production will treble (or more) and those frozen green rosettes will rise up from the soil and give us six more weeks of salad greens.