Not LAPD but LA Sheriff's Department.  Why does this not qualify as a charitable contribution (for benefit of local government)?  Probably, because he still owns the horse and trailer.  Mounted police are not that uncommon but canine units are a lot more common, and at least back in the good old days before they decided to defund the police by taking away tax deductions, unreimbursed dog expenses were allowed as EBE.  

Facts and circumstances.  How often is the horse ridden, outside of police duties?  How often is the trailer used?  And does feeding the horse, cost as much as feeding a horse?