Like many women (and some men too), I loved horses when I was a kid. I still do, though nowadays I am more likely to be running alongside my dogs as they race around an agility course than hurtling over jumps (or around barrels) on a horse's back. I never realized my adolescent ambition of owning my own horse, but I did work at a stable for a couple of years as a teen and I've taken riding lessons off and on since I was a kid.
One of the things that appeals to many people about traditional high fantasy settings is the notion of using horses as transportation. There is no doubt that mechanical conveyances are faster, not to mention easier to care for. But the emotional bond that can form between horse and rider has long been romanticized in folklore and literature.
Since most people living in the modern world have had only passing contact with equines, there are a lot of things that people don't know about these animals and a lot of inaccuracies that can creep into stories with horses in them. If someone is setting a story in an actual historic setting, or is trying to create a parallel world that is at the exact same level of social development as a historic period, the potential for anachronisms exists as well.
I thought I'd rack my memories, do a little research and put down some "fun facts" about horses that may be useful to anyone writing a fantasy (or other stories) where travel by horseback or in carriages is involved. I delved into my collection of Equus magazines for some of this information, and did a little web research for the rest.
How fast can a horse travel?
A horse can walk 3-4 mph (a league was once defined as the distance a horse could walk in an hour).
A horse can trot about 8 mph (though this varies with breed and conformation)
A horse can canter 10-17 mph
A horse can gallop 25-30 mph
A horse can only gallop at top speed for a few miles/minutes at a time and will have to spend some time recovering afterwards at a walk (just as you would after running a foot race). On a long journey, a rider typically alternates between walking and trotting and the horse will need some brief rests over the course of the day and a long rest in between. It can canter or gallop for brief periods, but this will be more strenuous and require more recovery.
A well-conditioned horse that is not carrying a really heavy rider or load could ostensibly travel up to 100 miles in a day, but this would be exhausting and not something the animal could do day after day.
For a horse on a long journey of several days, 20-30 miles in a day would be more sustainable. The load a horse is carrying, its overall condition (and the terrain) will affect this.
How much weight can a horse carry or pull?
Saddle horses typically range from 875-1300 pounds and can safely carry 15-30% of their body weight. Live weight (a rider) is easier to carry than dead weight (a pack) since riders can shift their weight to make things easier for the horse. So pack horses may show signs of stress when they are carrying 25% of their weight or more.
Horses can pull considerably more weight than they can carry. It is not too hard for a horse to be able to pull its own weight, and they can even pull several times their own weight for shorter distances. The size of the vehicle's wheels make a difference, with larger wheels being easier to pull than smaller ones but conveyances with smaller wheels providing faster acceleration and greater maneuverability.
Dray (or draugh/draft) breeds, such as modern Clydesdales can weigh more than 2000 pounds and stand 18 or more hands (a hand is four inches) high! The heavy horses used by knights were the ancestors of many of the dray breeds that are still around today, though horses (and people) tended to be shorter back then.
How much food and water does a horse need?
Whether or not a rider needs to carry grain for a horse will depend on how hard he/she is working the animal and how much forage there is along the way or if they are stopping at inns at night.
A typical diet for a 1000 pound horse doing moderate work would be 20-25 pounds of feed a day, most of which would be hay or grass (if grass, the weight will be higher, due to its high moisture content). Approximately 2-5 pounds of this would typically be taken in as grain (often oats or mixed feeds) each day, though this amount would vary depending on the amount of work the horse is doing and how much grass or hay is available. Horses do better with frequent small meals than they do with just 1-2 large meals a day. Horses that have adequate time to graze and are not being worked really hard usually do fine with just hay and grass in their diet.
A horse will drink 6-10 gallons of water a day on average, and of course if it is working hard or in hot conditions, it will need considerably more. It is not possible to carry enough water for a horse's needs, even for just a day or two. This means horses are not useful in very arid environments where there are long pulls between water holes.
Potential anachronisms in historic settings
Horseshoes: The inventor of the horseshoe is unknown, but they came into existence in the early middle ages. Horses that are not traveling a lot over hard/paved/rocky surfaces actually do quite well without shoes, but the invention of shoes did prevent excess hoof wear once people began to pave streets. Prior to the middle ages, Asian horsemen used leather booties when horses were traveling over rough terrain, and Romans sometimes fitted horses with leather "hipposandals." There is no record of people nailing pieces of metal to horses' feet until the 6th or 7th centuries CE. By around 1000 CE, cast bronze shoes with nail holes made an appearance, and iron horseshoes became widespread by the 13th or 14th centuries.
Stirrups. Although the horse was first domesticated around 4500 BCE, the saddle didn't make an appearance until around 800 BCE and the stirrup not until 200-300 CE.
Sidesaddles: Although there were prototypes available as early as the 13th century, they did not allow for easy control of a mount, and so European ladies often rode with split skirts or on pillion saddles behind male riders until the 16th century when a more usable design was developed.
Sources of Information