BUSINESS MILEAGE

You can deduct business mileage if you have a home office that qualifies as your regular workplace, and drive between your home and another work location in the same trade or business. If your home isn't your regular workplace, driving between home and work is considered a commute, and therefore isn't deductible

I don't think you need a home office.  You need to work at two places in the same day.  Then, the mileage between them is deductible.  So, at least one-way mileage would count if the cows get milked every day.  Have you checked Pub 225 to see if that situation is covered?  

When he does day labor elsewhere, is he an employee there? If so, that would be commuting.

He arises at his home in the morning, goes outside to the farm and feeds the cows, then drives from the farm to his off-farm job in town, works 8 hours in town, drives back to the farm, feeds the cows, then goes into the house.  It appears that his mileage to and from the job sites is all business mileage.