There are a few factors involved in The Carry. Interest rates being one of them. A quick'n'dirty method would be to figure on about 3 to 3.5 cents per bushel per month to store grain. This cost is approximate and can differ due largely to interest rates. (including opportunity cost of capital, interest on an operating loan for a farm, etc)
There is no "carry" in the meats, as you have to feed them daily regardless.
Hope that helps!
drewfus