Equine bone maturity: When can I start training a horse?

When can I start training a horse? (or variants such as when can I ride my horse? how young is too young?) is one of the most common questions asked in online horse fora, and one of the most controversial issues.

Table of Contents

Imprinting and working with babies
What to do with your two-year-old
Driving
When can I ride?
Reasons not to start at three
Will I hurt my horse?
Some questions
Is it always bad to ride a young horse?
Additional information

Before I begin, let me state that it is not my intention to take a firm position here. I know this is a controversial topic (see my post on How to discourage questioning in online horse fora). I usually stay out of it. But today someone posted one of the many Growth Plate Fusion chart links in one of my Facebook groups (Morgan Horses we Love). As usual it received many approving comments, and then there was my comment:

“Someone needs to explain to me why it is important to have the growth plates fused before training commences.”

Because many of the comments did not just claim the usual (no riding before 4-5, racehorse industry is the evil proof). Some claimed that any work at all, even long-lining**, was bad before 3 years.

**Here I would to some extent agree, since long-lining can involve many circles. If these are repeated and too tight, it’s not good… be the horse two or twenty.

Seriously, people are always claiming it’s terrible to ride a young horse (“young” meaning different things to different people… anywhere from < 3 to 6-7 can qualify as “too young”).

But no one ever says why beyond the standard “their growth plates are not yet fused.” The posted link (above and here) says only that it’s easy to sprain the back (displace the vertebral growth plates). And these growth plates close last, finalizing with the vertebrae at the base of the neck. Therefore, the short excerpt concludes, you should be very careful not let the horse strain its neck.

Very apropos, the piece adds that it’s important to train a horse before tying it so that it doesn’t pull back.

Given that many if not most horses are tied before they are ridden, this is important advice. I imagine many people who decry backing a horse before age 4 (say) do tie their horses. Ground work is so often offered as a replacement for riding.

But we are getting off topic.

When to start training a horse: Some answers

First, a link to the article cited in the growth plate link above: Deb Bennett on skeletal maturation and starting horses. (Her book, Principles of Conformation Analysis, is an excellent reference on equine anatomy.)

I first read that piece several years ago, and it’s still one of the best I’ve read. It explains bone growth, rate of plate closure, and the potential effects of early training on horses. It also includes Dr. Bennett’s views on the horse industry.

A note: In that piece, Dr. Bennett advises starting ground work at two, backing (hopping on for short times) at three, basic riding at four, and more advanced skills at five. This is indeed the traditional advice, and what I was taught. I learned in terms of Morgans: train to harness at two (start long-lining around 19 months). Ride at three. No jumping or strenuous work till five.

There is a lot you can do before riding though.

Imprinting and working with babies

As many people point out, you can start “training” as soon as the foal is born. Training can include “imprinting,” or desensitization of the newborn foal. Horses don’t imprint like birds do, but it is much easier to work with a relatively tiny foal. Teaching a small newborn to accept human touch all over its body is faster and safer than doing the same with a 1000+ pound fully grown horse. Dr. Robert Miller made imprinting popular, once upon a time. (Article on Dr. Miller and foal imprinting.)

Dr. Miller also wrote the introduction to my book, Cowboy Dressage: Riding, Training, and Competing with Kindness as the Goal and Guiding Principle.

Foals can and should be taught to lead and stand still for grooming, farriers, and vets before they are weaned. (That said, it’s really no big deal if they are not. It’s not hard to do any of this with am older horse, and most of us who have had many horses end up a bit lazy about early training.) You can teach them to tie as well, and at this age, it’s easy to use a belly or butt rope.

What else can I do with my baby?

If you want to do more than the minimum, you can teach foals/weanlings to load in a trailer. You can clip them (if you don’t think clipping is evil). You can take them on walks. Ride the mother and take them on rides. You can pony them. You can put tack on them (blankets certainly). Teach them to “model” for in-hand or halter classes.

What about your two-year-old?

This is where the anti-early-starting voices confuse me. I can understand why you would not want to ride a two-year-old. (Though I do not think it’s necessarily evil. The early age of riding racehorses is not the primary cause of the spectacular breakdowns that give racing a bad name.)

Why not train a two-year-old to harness though? Granted, a lot of small circles are bad for horses at any age. They are a lot more work, and put stress on the splint bones (and adjacent cannons). I’ve seen more horses pop splints going around in slow(ish) circles than going much faster on the straight. But long-lining allows for large circles. Ground driving (and driving, if you hitch) allows for no circles at all.

If there is some way driving can injure a horse, I want to know about it. Yes, over-bitting is problematic (even in older horses). Over-working is problematic (at any age). Mentally, a two-year-old might not be ready. Maturity is not only about growth plates.

Long-lining and ground driving need not be hard work, and can be used to ready a horse for any discipline.

Even if you never hitch the horse, teaching it to long-line and/or ground drive is very useful. I would use long-lining to gauge the skills of a horse: Does it set up for park or English Pleasure? Does it carry itself more like a hunter?

View this post on Instagram

Emma likes horse shows.

A post shared by Leslie Arnould (@akiramorgans) on Aug 1, 2018 at 2:23pm PDT

The next step, if you have the knowledge, equipment, and space, is to hitch your horse to a cart.

I grew up in the Morgan horse world, and traditionally, Morgans are shown in harness beginning at two. Standardbreds (and other trotting/pacing breeds) are raced at two; many compete until they are 8-9 years old. (US Trotting Association). Harness racing horses are far less likely to breakdown than Thoroughbreds (or QHs), despite the fact that they are broke to harness as yearlings, race at two, and have much longer careers than other racehorses.

Of course, most people may not have the knowledge or equipment to drive their horses, but if you do, it’s an excellent option for training and conditioning young horses.

Pulling a cart is work, although a light sulky or training cart on a groomed surface is not going to be much. A properly bitted horse pulling a cart on a good surface is unlikely to strain any vertebrae, and certainly isn’t bearing too much weight.

Regardless of when you start your horse, driving is a fun addition to its training. It works different muscles and does not put weight on the topline (for those who are worried about vertebral growth plate fusion and/or for horses that have issues). For those who want to compete, there are many options… and you can always do parades!

But when can I ride my horse?

The bigger question always seems to be when it’s safe to start training a horse under saddle. As mentioned above, three seems to be the traditional “okay to begin” time for most English-style disciplines. Many Western-style disciplines tend to start horses by two. Quarter horses are bred to develop quickly and look mature at a young age. Of course, it’s all muscle; their skeletal development does not differ from other breeds. In other words, whatever type of horse you own, the growth plate fusion timeline linked above applies.

A note on “age.”

Traditionally, horses are considered to begin a new year on January first no matter when they are foaled (in the Northern hemisphere). In other words, all horses born in 2017 turned three on January 1st, 2020. So horses born in July 2017 (or even December) are, for showing and racing purposes, three now. So it’s always a good idea to breed your mares to foal as close to January as possible, weather permitting.

The American Endurance Ride Conference (AERC) counts age from date of birth. Horses must be 48 months old to compete in limited distance (25-35 miles). They must be 60 months to compete in endurance distances (50+ miles), and 72 months to compete in a single-day 100 mile ride. (What about a 40-mile ride??)

A lot of the pro-(very)late-start advocates are endurance riders. It is interesting to me that a horse that must be 5 to compete in endurance (6 to do 100 miles in 24 hours) has to have been in training for at least two years. At least, I wouldn’t want to ride 50 miles on a horse that had been ridden for less than two years. This means starting at three.

Of course, driving is a great way to leg up a horse for riding long distances. Off-track Standardbreds can make great endurance prospects. But most endurance people probably ride preferentially.

I personally see no problem with riding a horse at three, provided it is done properly.

Why not start riding at three?

The primary reason I wouldn’t start riding (or even driving) a three-year-old is that it may not be mentally mature enough. Or I may put a month of training on a horse that’s around 3 years old, decide it’s not ready, and put it out to pasture for a year. Horses don’t forget, and a silly 3-year-old baby brain that spooks at every shadow might be steady and easy to train at four (or five).

On the other hand, it has always seemed to me that younger horses are easier to start (compared with horses that are 8+ years old). That’s why I prefer to start training a horse – both on the ground and under saddle- before it’s five. But that’s just me. I know many say it’s easier with older horses.

But am I going to hurt my horse if I ride it before its growth plates are all closed?

I don’t think so, provided you do not overwork the horse, but then, this is the question. It is undeniably better to have a lightweight rider at first. This is true for young horses, and even older ones. It takes time for the muscles to develop enough to carry the weight of a rider.

(The saddle is also important. Some heavier saddles distribute the weight better than lightweight ones. A poor fitting saddle will naturally do more harm than good.)

Note that I am thinking about vertebral plates here. By three (when I would ride), the lower limb plates will already be fused. The scapula and humerus will be by four. Many people tend to think of lower leg injuries associated with early starting. Racehorse trainers may x-ray knees to make sure those plates are closed. But if your horse injures a lower leg, chances are it’s not due to early riding.

Some questions:

Given that exercise encourages bone restructuring (and strengthening), is it not beneficial to do controlled amounts of conditioning early? Bones are not dead, even after a horse is skeletally mature. And older horses also pop splints and break bones and soft tissue. In my experience, injuries have always resulted from over-training (or plain bad luck) at any age.

It seems the jury is still out on when, if, and how exercise can aide in desirable bone development, according to Kentucky Equine Research. However, there is evidence that long-term exercise (compared to a control group of non-exercised horses in pasture in this study) results in greater bone density. The authors conclude this is independent of age (Rajão, Leite Nogueira, Godoy, & Lima , 2019). Note that in humans there is an abundance of evidence that exercise improves bone mass.

Yes, there are many breakdowns in racing. These horses are started around 18 months, and worked hard at two. Most breakdowns involve the lower limbs. Mostly, these growth plates are closed by the time intense training happens. I saw surprisingly few topline injuries in Thoroughbreds (or racing Arabians) when I was riding and racing. On the contrary: race horses tend to develop very strong toplines. It’s the galloping. Of course, the riders are lightweight, and they stand in the stirrups to gallop (most of the time).

So the question is, can riding be beneficial by strengthening the topline? Clearly, I am assuming proper saddle fit, rider weight, and exercise tailored to the horse’s fitness level.

The MAIN question (for the anti-starting young crowd): Is it always bad to ride a young(ish) horse?

Can it never be beneficial? Can you explain to me exactly why it’s always a bad thing to start training a horse under saddle before it’s completely done growing?

We can all agree that putting a horse in a position where it will hurt itself by straining its neck/back/etc. is bad. Tying a horse to anything can be bad. Leaving it in a blanket where it can get tangled up can be bad. Leaving it in a padded box can result in catastrophic injury for that matter.

We can also agree that asking a horse to do too much too soon is also bad. Always, at any age, in any type of work. It is bad for the horse physically and mentally. It is counterproductive.

But is riding a horse that is less than 6 years old (ie does not have every growth plate fused) always a bad thing?

One reason to start horses at a younger age is that soft tissue is more elastic and remodels more easily. Strengthening tendons may be easier and less risky in young horses (Dowling, Dart, Hodgson, & Smith, 2010; Smith & Schramme, 2003).

Additional information:

Some references to use if you are interested in more information:

If this book weren’t so expensive, I would buy it to use as a reference: Equine Exercise Physiology. This one is more affordable. They might not tell you exactly when to start training a horse, but they will help you understand the underlying mechanics.

As a side note, there are many empirical studies that provide evidence that turnout is essential to maximize bone development in young horses. Confinement in stalls at any age is best avoided, but it can seriously limit bone development in younger horses. Bottom line, exercise really matters for foals (e.g., Cornelissen, van Weeren, Ederveen, & Barneveld, 1999) especially.

Some resources suggested on Facebook:

Conditioning Sport Horses (Hilary Clayton)
Conditioning Young Horses (The Horse, 2018)
Racing start for two-year-old thoroughbreds not detrimental (University of Sydney, 2018)
Kentucky Equine Research Study Benefits Bone Density (Another from Kentucky Equine Research, 2018. Remember, they sell stuff.)
Great podcast about the benefits of sprinting young animals (they used calves as models for horses).

Please share your opinion in the comments!!

Many thanks to Leslie Arnould of Akira Morgans and Cece Green Yelek of Greentree Ranch Morgans for use of photos and videos of their beautiful horses.