'They should all be getting exercise no matter how old'.
I don't think so.
There are horses that have to be retired due to injury and are just put in more pain by exercise. Sometimes even hobbling around a pasture is too much for them.
Here's kind of a 'sliding scale of retirement' - each option is geared toward the horse's individual needs and condition.
1. Continuing on at the same level of work
2. Continuing in work, but at a slightly reduced level (time, intensity, speed, skills, how demanding the surface is, tightness of the patterns, can be reduced)
3. Being ridden by beginners no more than 3 hr a week - just enough to maintain fitness, and most work is at walk and trot.
4. Being ridden by a lower level rider for 15 minutes at a time at a walk, on level surfaces - not hard, not too soft, no sharp turns or small circles - some old horses require a more expert rider to keep them balanced, prevent tripping, or be disciplined enough to avoid activities that would aggravate the horse's condition.
5. Being hand walked or if quiet, turned out for several hours a day on a smooth, supportive area - depends on condition of legs - if a chronic injury or weakness exists, horse may have to go out in a smaller paddock or in a situation where the animals stay quiet and don't run
6. When it gets to the point where the horse is too fragile to leave its stall, it is not enjoying life, it is not eating well due to bad teeth or simply too much discomfort any where to eat, pain is unmanageable, horse is panicking due to its lack of mobility (not all age gracefully), it's losing use of its legs it is time to consider euthenasia.
Our old horse is very prone to dehydration at any time of year. He suffers a great deal in hot weather and colics easily. He requires soaked hay and electrolytes to keep him getting enough fluids. We keep him indoors during the heat of day, and he requires several baths a day and a fan to keep cool. We purchased a companion for him as he needed company, and he is getting a little anxious when his companion is not in sight. The veterinarian says it's impossible to tell if his anxiety is due to senility or vision changes, or both.
He has a ligament injury and cannot be ridden above a walk or risks injury as he swings the leg inward to avoid putting stress on the ligament. As mentioned we think his vision is starting to change (age 17) so he trips frequently - therefore is not extremely safe to ride.
He has never been a 'high maintenance' horse when young and never needed any special care.
Now he does.
We do what he needs.
On the other hand my friend has a Welsh pony who is nearly twice my horse's age, and he's just as energetic as ever and hasn't had any reduction in work - but his work is easy - he just does 'up down' lessons about 3 times a week and that's all he's ever done.
Horses can be very, very different, despite being the same age, even the same breed or type. How each animal ages is individual.
What is done with the old horse has to be a highly individualized, well thought out program, put together by consulting with a veterinarian if need be. The idea is to have the horse as comfortable as possible for as long as possible.
