Sorry, I misunderstood the first couple of questions. I meant that each type of feedstock is worth the same: 1 unit of grain is worth 1 of hay is worth 1 of roots. Different types of animals do eat different amounts. In the barn panel, you see a number for feedstock, something like 120/150. The numerator is how much you have in that barn, the denominator is, I think, the estimated yearly consumption of feedstock in that barn. Which is really the same thing as the winter consumption, because animals only eat from it for the 3 winter months.
If you want all the numbers I pulled from the game: