Can I deduct the cost of cat food donated to my local humane society?

Yes, if you are itemizing your return, the cost of the donated cat food would be deductible as a charitable donation. 

But where does the deduction go in the program?  Pet food is not listed under the Pet category.  Would you convert to the cash value?

You would enter it as a donated item in the charitable contribution section

1. Deductions and credits
2. Charitable donations
3. Donations to charity in 2021
4. add charity
5. select items
6. describe the item
7. you get credited for the dollar value amount of the donation