I would like to talk about the nature of horses and how your off-the-track Thoroughbred fits into the scheme of things. Horses are grazing animals. They are animals that are not hunters, but the subject of the hunters - the prey of the predators. As such, they are finely tuned into personal salvation - flight response - in order to survive. Nature has given horses the extreme ability to GO AWAY from anything percieved as a bodily threat. They have eyes on the sides of their heads the better to see around them as they graze with their heads down. They have powerful bodies with long legs and big hindquarters to push off and run fast. They have keen smell and hearing. If you take all these qualities today and then encourage the competitive nature of the young horses, put them together on a smooth level surface, and let them run, you have a racehorse.
That being said, as a new rider to your OT TB, what you are now about to do - teach the horse to slow down - is not only contrary to his nature but also to his training up to this point in his life. You are the progenitor of much change by your very presence! Here's some of the differences you are going to be making and how bewildering this is to your horse:
1. Feed. It's likely you'll be dropping his grain and upping his hay - and there will be slight differences in what kinds of grain and hay you'll be feeding. This is the most important change, since some of the research involved with the No. 1 horse killer, colic, indicates change in diet over 50% of the time can lead to colic. Not only that, but the time you feed will also be different. Racehorses are fed 4-5 a.m. so they can work at 6-7 a.m. Then again at 11 or noon, and again at night. Most pleasure people feed at 7 a.m. then go off to work all day.
2. Attention. Racehorses have their busy time in the morning, where people come and go, and horses are moved out of the barn, and back in, exercised, etc. Afternoons and evenings are quiet. You probably work. So evenings will be his busy time with you, an opposite schedule of his life to date. He will feel abandoned and neglected without the familiar morning attention; when you finally show up at night, horses can go thru a period of depression due to changes in routine.
3. Physical Activity. Not only have the changes above taken place, but now you will take an animal that has had individual attention and kept in a stall and throw them out with lions and tigers (in a pasture with other horses). Suddenly he will have to remember his body language and interaction techniques with other horses (or learn them quickly if never pastured with others). This involves a great deal more low-level physical activity than he is used to - walking, moving to graze, keeping away from or trying to stay with other horses in the pasture. This is why turn-out should be gradual and in incremental increases each day - to carefully introduce the pasture buddies one at a time, and increase the turnout time a little more each day until he's comfortable with new friends and with the increased physical activity. Sometimes with an injured horse that must be kept in a paddock by themselves, this increased time helps his spirit, but only if he's not anxious about other horses around him.
4. Training. To date, your OT TB for the most part has had a crash course on breaking and there it stopped as soon as he got to the track. He's uneducated to the hand, leg, or seat. Now you've come and put a much heavier saddle on his back; an unfamiliar bit in his mouth; and you take much more time to get on him than those light jockeys. Once you're up, you just hold onto his mouth and walk about, so unlike what he's always done before. Where's the track? Aren't we supposed to get going here? Why are you sitting on my back? Exercise riders and jockeys always get up off the backs of the horses. They are allowed to canter or trot slowly at first, it doesn't matter if they are sideways or chucking the head, then gallop from there. The horse doesn't understand the difference in the gaits because they are allowed to go what they want and fall into the gallop, really. Now you are telling the horse, there is a difference in how you do this gallop stuff, in fact, I want a canter - a much slower gallop, in fact, for some horses a gait they've never developed. And if you are sideways, I'll straighten you up with the reins. And this is an arena, you must turn all the time, very little in the straight, wide open department now. All of this is quite foreign - very different - and you must take time to be understanding of what he's had before as opposed to what you want to do now. Do you shop at the same store? Go to the same bank, post office, gas station? How would it feel to suddenly be told you can't do that, you must go to a different store, post office, bank, gas station, in a different part of town, with a different set of circumstances. You'd be startled and annoyed until you go used to it, too.
Once a horse learns something, and is good at it, he becomes proud of what he knows and of his routine and environment he's comfortable in. When you come into his world, you change all that. Perhaps he was injured before you got him. So not only was he off the team, and maybe in pain, but you came along and took him out of the only world he's known. You call it a rescue but he calls it something different, and may see you as representative of this new topsy-turvy world where he doesn't know anything and begins at the bottom of the pecking order. So you must be his friend and protector. How do you convince him you want things to be better? Start with the four listed items above, and pay attention to his needs.