Re-calculating Hay Needs

The farmer asked if I wanted another wagonload of hay for the winter. Four months ago, I would have said no, that I had plenty of hay. However, the dry weather makes me re-calculate. Even in the snowy, cold months of December, January and February, the horses and sheep find forage in the pastures to supplement the hay that I feed them. But, with no late summer and fall growth, that isn't the case this year. So, I'm calculating their feed needs as if they have no other food source -- something I haven't done before. If the winter is unusually cold, their food requirements also increase. I asked for another wagonload of hay. There's a good chance I'll need another load come early spring.