Don't even try it. When I operated a tiny riding academy (1985-1994) I was audited twice. The IRS REP told me that if you show or breed they "red letter" your tax returns. I was profit oriented, so I made it through without owing anything. DH and I kept receipts and practiced good record-keeping. Money is so tight that I think I would be owing them now if I still operated my business. It's just NOT worth the trouble. HOWEVER, we did "adopt" a gelding from a rescue in 2010 and deducted him.
Does not really make my horse "tax deductible" but it does help have a buddy for him without having the expense of another horse -- I board one. The amount I charge is just little bit more than his feed to help compensate for my full-time care and he keeps my guy company.
I have 3 acres and am having a no climb horse fence put in right now, I also bought 2 horses from a rescue group. Can I deduct my horse fence and my rescues?