The environment we choose for our horses to live in, is extremely important and serves as a foundation for everything else. We can make great efforts to be gentle and kind to our horses in training and riding, but if the surroundings they live in do not support their natural needs, we will never have healthy, happy, well-functioning horses. Environment comes before everything else.
In order for us to create a good living environment for our horses, we must understand what natural needs the species have and do what we can to replicate their natural habitat. The main factors we need to pay attention to when designing our horses living environment are:
Diet, movement and social life. 

I advocate for track systems as an excellent way to keep horses in domestication. 
With a track system we can replicate the horses natural environment in a mini version, and we don't need huge amounts of land to create a well functioning track system. What we need is an understanding of the natural needs of horses and a good portion of creativity when we design our paddock. 

If you wish to create a track system and need advise on how to do it and which elements are important to implement etc., I can help you.
If you are in a situation where a track system is not a possibility, I can help you find other solutions to give your horse the best possible life in the situation present.

Diet

Horses are herbivores and prey animals.
they are designed to move about at a calm pace all day long searching for food, water and minerals.
Wild horses eat a large variety of plants and move over a large area to find enough to eat. 
horses have a relatively small stomach and very long and large intestines. This means that they are not meant to eat large meals, but rather be trickle feeding, eating a little bit at a time, spread out over the day and night. Wild horses spend about 16 hours a day eating.
A horse's digestive system is designed to break down large amounts of fibre. Both the horse's stomach and hind gut are dependent on an almost constant supply of fibre to sustain a healthy balance.
Horses also need carbohydrates, but in small quantities.
Too much sugar and starch will alter the balance of bacteria in the horse's hind gut and cause a myriad of problems.

A species appropriate diet for horses is a high fibre, low carbohydrate diet with great plant variety. Giving our horses 24/7 access to good quality hay with many different plants, serves as an excellent basic diet.
Since it is very difficult in domestication to replace the selection of plants that wild horses have access to, we must add a vitamin/mineral supplement to the basic hay diet. 
It is import to also make sure that the horses always have access to salt.


Having many different plants, herbs, trees, bushes etc. in the track system for the horses to nibble on is also a good idea, to keep the environment interesting and stimulating for themGrass in controlled quantities can serve as a supplement to the basic hay diet.
Some horses tolerate grass better than others, and the carbohydrate content in grass varies enormously depending on many different factors. 
Because of this we must treat grass with caution and view it as a supplement to our horses basic hay diet, rather than letting the grass be the main diet.
It is also important to know your individual horse well and how well he/she tolerates carbohydrates.

In a track system we can provide our horses with 24/7 access to hay in feeding stations spread around the track to motivate them to move in search of forage, water and shelter, just like they do in the wild.

Movement

Observations of healthy populations of wild horses show us that they live in areas where food is scarce. This means that the horses need to walk many km every day in search of food and water.
Horses are designed to be in an almost constant flow of movement and the calm and quiet but constant movement through varied terrain keeps their bodies strong and healthy, and the motility in the digestive system working properly.

Horses are prey animals and designed to be able to run fast to escape a predator. An average horse can hit a top speed of 50 km per hour.
Being able to run at such a speed in a split second, requires very strong and resilient bones, muscles, tendons, ligaments and
hooves.
In nature, the horse has to always be ready to run if a predator shows up, ready to run without a warm up!
Horses need to be in an almost constant flow of calm, relaxed walking about for the whole physical apparatus to be ready for a sudden fast outburst of energy when needed. It is not just about getting enough movement, but also about getting different kinds of movement. Up and down hill, over and around obstacles, moving over uneven ground and different kinds of surfaces. 
all of this strengthens bones, muscles, tendons, ligaments and hooves.

Movement is also needed to keep a healthy blood flow in the horse’s hooves.
When the horse is loading the hoof, blood is captured inside the hoof capsule. When the horse lifts the hoof off the ground, the blood is pressed back up the leg and back to the heart. Movement is vital for this pumping function to work properly.
The blood brings nutrients to the cells in the hooves and it takes away with it waste products.

For an animal designed to move and designed for flight, being locked in a small space is stressful. Not all horses show mental stress on the outside, and we have to be aware of the affect an unnatural lifestyle can have on the horse's health and wellbeing, both physically and mentally. 

Social life

Horses are herd animals and highly social creatures.
They need to live in a herd with other horses to thrive and be mentally balanced.

In the wild, being in a herd means safety. When you are in a group you have better chances of survival than if you are outside of the herd alone. This is deeply ingrained in our domestic horses as well. Horses feel safe and secure in the company of other horses.
They can learn to be alone for a while and stay calm, but they should never live a life alone.
Horses can have friendships with other species of animals, but they should always live with at least one other horse.
Other species cannot replace the company of other horses, as they don't speak the same language.

Social life is not just about safety and security for horses. They enjoy each others company. Play, mutual grooming, eating together, resting together, swiping insects of each others noses with the tail, bickering and arguing are all natural elements of a horse’s social life.

Living in a herd also has a positive affect on the horse's way of moving. Horses living together tend to move more, and in many different movement patterns because it is part of their social interaction.