I agree with Hmmmmm and GlitterIsMyDrug--first find out if gifts are indeed being exchanged; if they are, then make a casual suggestion for a pet store gift card "or here's a link to my Amazon wish list" of pet items.
With the initial wording, I would be very put off, for reasons others mentioned. I didn't even pick up at first that the gifts were not really donations to an animal shelter, they are gifts to you to be used for the pets you have chosen to take in. Which is a great thing to do, but the initial wording seemed a bit high-handed.
I would try to be more casual about it, wait until asked or at least until gift-giving intentions have been established, and not go into the details of your wants--some people would like baking supplies, some people would like books, you would like pet supplies. It's stuff for your hobby/interest, like everyone would like to get.