Solution 1: genetically engineer the horse to enhance its intelligence. Teach the horse a college level of English language comprehension, so that the horse can understand commands like "It is time to vector your course in the widdershins direction", "go thataway, stupid!", or whatever phrasing suits the passing fancy of the farmer at that moment. Problem will be solved after a few decades of over engineering, and each draft-horse will cost a quarter of a billon dollars.
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@david_chisnall
Solution 2: take an off-the-shelf draft-horse. Teach it that "Haw" means turn left and "Gee" means turn right. Teach the *farmer* to employ this user interface when directing the horse. Problem solved.
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