I have often seen first responders who get a uniform allowance or equipment allowance (including firearms and ammunition) not paid under an accountable plan, so added to the W-2.  Which at least increases the basis for figuring pensions.  When the law changed, first with the 2% cut and then the 100% cut, some departments set up accountable plans, but others did not.  

There's a deduction for federal if you can work it into out-of-pocket expenses for government benefit. If his job does not require him to have a horse, then he is just volunteering its use, along with the trailer.