I was aware of this tax decision two years ago (I'm a legal secretary and am interested in estate planning and taxes). My CPA successfully claimed as a charitable deduction expenses associated with my taking care of an (outdoor) cat colony for tax year 2011and 2012. Food alone was over $1,000. I did NOT claim expenses associated with spay/neutering because I paid about what it cost the organization to get them s/n, i.e., $50. I might have chanced this but didn't want to push the possibility of an audit. Over this two year period, I TNRd around 25 cats.
As indicated above, DO follow IRS regulations closely: you must have a letter from an organization (501(c)(3)) saying you help them with their organization's cause (be it fostering/TNRing/educating); the letter should be dated on or around January 1. I drafted the letter and emailed it to the sponsoring organization to place on their letterhead. Ask them to mail you the original letter; keep the envelope with the postmark.
And you MUST keep original receipts and be able to prove what those receipts are for. Most grocery stores now indicate exactly what you bought, e.g., Friskies, Giant brand milk.