You will determine the Fair Market Value of the hay bales at the time that you donated them. Per the IRS Fair Market Value is defined as such:
"To figure how much you may deduct for property that you contribute, you must first determine its fair market value on the date of the contribution.
Fair market value. Fair market value (FMV) is the price that property would sell for on the open market. It is the price that would be agreed on between a willing buyer and a willing seller, with neither being required to act, and both having reasonable knowledge of the relevant facts. If you put a restriction on the use of property you donate, the FMV must reflect that restriction."
What Is Fair Market Value (FMV)?
It would be best to find the Retail Price of these Hay Bales and create and keep this in your records. The most ideal record to prove this price would be an advertisement for the same product or even better a letter from the organization that received the donation placing a value on your donation.
