If you purchased these items new and turned them over to the Humane Society for use, I would advise that you treat the purchase price as a cash contribution.
For substantiation of your deduction I would suggest that you (1) save copies of all the purchase receipts for such items and (2) obtain a receipt or thank you letter from the Humane Society acknowledging your purchase of these new items for their use, and indicating a value that corresponds to your purchase receipts.
