Can we use apple wood...

to build our cat tree/scratch? It will have natural parts of the wood exposed and also will have carpet, sisal, etc...

If I get an answer tonight we get to go pick out the branch to design it. We had an apple tree cut down earlier this year!

I don't see why not. I love to use apple wood prunings for both the wood burner and to add to a BBQ. I even used some thick prunings one year, along with chicken wire, to make an emergency garden gate, and sometimes people would stop & ask me where I bought the gate

I would assume that it would be safe, but just to double check, please go to the aspca's website and check on the list of posinious plants/trees just to be sure . If they don't have it posted, you can call their hotline or consult your vet. I'm sure it's safe to use though.