I have always been amazed by the fact that some of the world’s biggest and most powerful animals subsist on some of the most (seemingly) nutritionally pathetic food imaginable.
This is particularly remarkable in the case of horses. Cows just stand around all day, but horses are so powerful and swift and used for so many high-calorie-consuming tasks I find myself wondering:
Absent modern day high-density feed, (i.e., corn) are horses genuinely capable of sustaining long days of riding or pulling? How many hours do they need to spend eating grasses and hay and the like? How many calories does it take to maintain basic health for a horse, vs. how many calories it takes to keep them working hard? If a horse is pushed, how long can it keep going without food?
Also, how much sleep do they need? Do they really sleep-sleep, with REM? I know that carnivores do, at least dogs do, so I assume other carnivores do. But since horses and cows and other prey animals “sleep” standing up, it seems hard to believe that they really sleep as deeply as other animals.
Another “Thing that amazes me about horses” is the spindliness of their legs in proportion to their bodies, at least to the naked eye, and how those odd ratios actually lead to incredibly powerful and fast runners. To my own eyes, their legs appear to barely have any musculature at all, much less the kind that leads to the power and strength and speed they are capable of.
Much of the skewed ratio is a result of modern breeding. If you look at wild horses, they aren’t nearly so spindle-legged. And besides, a round barrel torso and skinny-but-powerful legsis pretty commonin herbivores. They need that big, round gut to process their food.
Horses in the wild mostly spend their days grazing, and occasionally running away from danger. They aren’t pulling loads or carrying weight - tasks that require the modern high-energy feed you mention. But because they’re not spending time as well as energy pulling/carrying, they have time to graze most of the day, cropping enough grass to eat.
You aren’t mistaken. A horse’a lower leg from the “knee” down (what appears to be the knee in the foreleg is actully the carpal (wrist) joint, and the patella in the hind leg is actually up by the torso, not in the hock) does not contain much muscle. The tendons of the lower leg act like a “slingshot” to amplify the power of each stride. This allows the horse to “recover” 35-40% of the mechanical energy expended in taking a step.
Non-domesticated and feral populations of horses have more “bone” (thicker leg bones) but they don’t have more muscle.
A horse’s digestive system is made to consume constantly. A horse can become very sick, and quite easily die, if does not have access to forage. On a normal day a horse will spend part of every waking hour grazing. ETA: 2.2 pounds of hay per 100 lbs of bodyweight is the rule of thumb for domestic horses. Hay weighs a lot less than grass, since it is dried. An average sized horse is 1,000 - 1200 lbs.
Horses are also extremely lazy. When not threatened by danger and not fighting for breeding rights, they just stand around, eating. Having lived on a horse farm for two years, domesticated horses are seen spontaneously running about very, very rarely. Typically they only frolic when they are alarmed or excited by something specific, such as a whole crowd of horses cantering by when the hunt passes through, or nearby fireworks, or extremely unusual events, like a couple of feet of snow in Virginia.
Okay, so do we have any idea how, in the days when horses were transportation, their needs were met? Especially for long distance travel? Did they travel an hour, rest an hour, travel an hour, rest an hour? Can horses catch up at night if they didn’t eat at all during the day?
Oats and corn are extremely calorie-dense compared to grass or hay. Slide a feedbag full of grains over their nose when they’re not actively working, and you get a lot more energy into their system a lot faster.
(Also, working horses back in the day may not have, shall we say, lived as long as their potential lifespan can reach…)
Back in the day (which was as recently as the 1950s) a horse over 12 was so old you didn’t even bother to say the age, you just said “aged.”
Today, 12 is considered the prime of life for a horse, and working into their early 20s is not unusual, even at a high level of competition. Understanding of horse nutrition, as well as general veterinary science, has advanced a great deal.
And contrary to what you might expect, large working draft breeds do not necessarily have to be fed more than smaller riding breeds. Often, they have to be fed less. Giving rise to the term “Easy keeper” for a horse that puts on weight easily. Often a draft or pony breed that is, like the Shetland pony, native to marginal grazing lands, or a cross with such a breed.
Just one more thing to add; feeding horses grain and legumes (also known as “concentrates”) is not a “modern” invention. Romans grew and fed concentrates for fodder for their cavalry, including alfalfa (which looks like grass hay, but is actually a legume), barley and vetch, and in some places, oats.