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Has Your Horse Stopped Growing? Stages and Signs to Know

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When I recently visited my neighbors’ barn I was surprised at the size of one of his three-year-old horses, I hadn’t seen it in the last six months. His size made me wonder if he finished growing or is he going to get even bigger.

Horses’ bones generally grow until they are six years old — however, the bones that affect height commonly mature at an earlier age, four-years-old. The only way to confirm a horse has finished growing is by x-rays.

A horse’s age and genetics give you most of the information to determine when a horse has stopped growing. But a lot of other factors need to be considered in the development and growth of a young horse.

Picture of a young grey quarter horse near water.

Horses grow fast compared to humans.

It is critical to young horses’ health to know the stages horses grow. Horses grow until they are six years old. However, they typically reach their maximum height at four or five years of age.

The bones of horses have cartilage on either end of each bone in their body, and as the horse ages, the bones fuse, creating a bond. The bones are used to determine the stages of horse growth.

A horse’s knees commonly close when they are two years old; however, you need to have them x-rayed to confirm. Most owners and trainers check their horse’s knees before breaking them to ride.

A horse’s knees close around two years old.

Checking young horses’ knees prevents some weight-bearing injuries. If a horse’s knees are not fully closed, the horse shouldn’t be ridden. The knee cartilage doesn’t provide enough stability to carry a rider.

Bones in the neck and spine of a horse continue to grow until a horse is close to six years old. Once the vertebrae have developed fully grown, they will fuse with the other vertebrates. And the horse has officially stopped growing.

Click on this link to view an interesting bone growth chart. The chart provides a picture of a horse skeleton indicating the particular age bones develop.

A horse’s growth slows after two years old.

Horse’s growth slows down substantially from two years old and beyond.

At two years old most sport horses are broke for riding, and they’re going through a training routine. From two to three years old, a horse is considered to be an adolescent. They are still growing and playful.

Horses reach 75% of their height before they’re one year old.

The much-anticipated foal has arrived. The baby is a healthy colt that stands easily within the first three hours of birth. So what markers can you expect your horse to reach in the different stages of his growth?

A foal grows extremely fast during the first stage of his life, and he’ll reach 75% of his mature height by the time he is two years old. You can literally see them change from one day to the next. It’s crucial during this period for you to provide the necessary environment for his growth.

Picture of a yearling, still growing.

Horses reach 90% of their mature height between 18-24 months.

As you monitor your horse’s growth, you want to see steady, moderate growth. Steady growth is optimal to avoid developmental problems associated with bone growth. When a yearling reaches eighteen months old, he will be ninety percent of his mature height and weight.

Concentrated feeds or pellets should always be weighed before feeding to a weanling. Three percent of the horse’s body weight should be fed to a young horse, and the feed can be a combination of concentrates and high-quality hay-like alfalfas.

Specialized feeds are commercially produced to provide a proper balance of minerals and vitamins for growing horses. Click here to shop for feeds on Amazon). Amazon is convenient; however, commercial feed is much cheaper at your local feed store or Tractor Supply Company.

During this growing stage, as in the first stage, it is vital not to overfeed your young horse. Overeating not only leads to the overdevelopment of bones but can also cause long-term gastrointestinal issues.

Picture of a two-year-old horse
Two year old Thoroughbred

Horses start to look mature by two years old.

Between eighteen months and twenty-four months, a horse reaches ninety percent of his mature height, by two years old he will have filled out and have a mature-looking body. However, he is still developing, both emotionally and physically.

Diet is still essential and overfeeding is an issue to be aware of. Provide good quality hay and feed. A clean water source is vital, and horses tend to drink a lot during this stage. If you intend to start working your horse, you will need to adjust his feed to maintain his body weight.

We had been meaning to pick up the pace for our two-year-old colt’s workouts, but first, we needed him checked out by the vet. The x-rays showed that he wasn’t ready for heavy exercise so we turned him out and will bring him back for training in a couple of months. Hopefully, his knees will close by then.

Since our two-year-old, pictured above, grew so fast we wanted to start picking up his workouts. But first, we got the vet to x-ray his knees to make sure he was ready, however, they were open, and so we turned him back out in the pasture.

Four-year-old horses are considered adults.

Once a horse reaches four, they are considered an adult horse. Between four years old and five years old, a horse will stop growing any taller.

As a horse reaches six years old, he is likely fully grown, the only way to confirm this is with an x-ray.

Picture of a chesnut baby horse.

Foals gain 1-3 lbs per day.

A young, healthy foal will gain from one to three pounds per day. Within two hours of birth, the foal will nurse — the newborn needs colostrum provided by their mother’s milk to prevent some disease and digestive problems.

A healthy foal will take in approximately 25% of its body weight in milk per day. You mustn’t overfeed lactating mares. A foal needs steady, sustained growth for proper bone development.

Grain can cause a foal to grow too fast.

At about two weeks old, the foal will start picking at his mother’s feed. It is essential to control his feed intake. Too much feed can lead to overgrowth of bone in the foal. If you notice him overeating feed raises the feed bucket beyond his reach. At two months, he can begin to eat small amounts of feed.

Monitor the weight of the colt and make adjustments accordingly. If you notice the foal growing too fast consider weaning him. Foals can be weaned as early as their third month.

It is also good to provide good hay to the young horse during this early stage, a mixture of grass hay and alfalfa provides needed nutrients. Weanlings can benefit from a supplement of vitamins, minerals, and protein in their diet. To learn more about the proper feeding of horses you may want to read this article.

Monitor your foals’ height.

Measure your foal from the floor to its withers to monitor his growth. An overfed foal can grow too fast and cause damage to its bones, resulting in leg deformities, such as uneven limbs.

If limb deformities are caught within the first couple of months, they can be corrected often with minimal intervention. This article provides helpful information about measuring your horse.

Have a clean, safe, and sturdy shelter available for your foal to escape the weather. Don’t keep a foal housed in a stall or small enclosed area for an extended period, never more than 10 hours per day.

Pasture time for the colt will increase his overall well-being. The ability to run freely is essential to the development of bone and muscle; exposure to other horses also helps develop social skills in the young horse.

Have your foals’ feet checked and trimmed by a farrier experienced in caring for foals’ hoofs. Proper foot care will help your young horses’ bones develop correctly.

Weanlings gain 1.5 lbs. per day.

Your foal has grown nicely because you provided him with the proper tools he needed, nutrition, exercise, and health care. At six months old he now stands approximately three-quarters of his mature height and weighs a little under fifty percent of his adult body weight.

Weanlings continue their growth spurt; at six months, you can expect them to put on about 1.5 lbs. each day. The amount of weight they add to their frame decreases with age.

At twelve months a yearling should be adding about one pound per day and at 18 months of age, the amount of daily weight added should drop to three-quarters of a pound.

Healthy horses follow a steady growth pattern.

At six months old a weanling will measure in at seventy-five percent of his estimated height when fully grown. In a year he will stand about 90 percent of his expected height at maturity. Growth should occur in a steady pattern. It is essential to keep a log and monitor the horses’ growth.

Exercise is essential for horses’ physical development.

The housing principles are the same for weanlings, foals, and yearlings, the more pasture time the better-adjusted horse. This principle applies to the physical and mental health of the horse.

For optimal physical development, a horse needs to run and play. A young horse’s bones, joints, and muscles require natural movement to develop correctly. The benefits gained in free exercise can’t be duplicated with the use of a walker or by longeing a horse.

Bone density, joint flexibility, and muscle growth all develop better in a natural environment. Studies have indicated that horses confined at a young age are more likely to become cribbers than horses not stabled young. For the betterment of growing horses keep stall confinement to a minimum.

Young horses need a series of vaccinations.

The vaccines necessary for your horse depends on the region you live in; however, there are some vaccines common to all horses regardless of area, these include Coggins, Tetanus, West Nile virus, rabies, Eastern/Western encephalitis, and flu.

Talk to your local veterinarian to ensure your horse has all the vaccinations he needs. When speaking to him about vaccines also discuss a protocol for worming your young horse.

Have all young horses’ teeth checked every year and also, keep up with your horse’s hooves. During the first two years, you want to maintain proper balance in your horse’s feet, so he doesn’t develop any unbalance in his limbs caused by uneven hoofs.

Turnout time is critical in the development of a horse.

Pasture turnout is essential not only for continued physical development but also for social and psychological considerations. Horses with more turnout time are easier to train. Keep up with the proper maintenance of the horses’ feet, teeth, and vaccine protocol.

The knees, in most breeds of horses, close between eighteen and twenty-four months of age in a horse. Closure of the knee is one indicator people use to decide if a horse is ready for training.

But be cautious and use information about horses as a general guide, remember a horse is an individual. You can’t use a one size fits all method to determine when a horse is ready to train.

Below is a YouTube video showing how you can use a string to determine the future height of a horse.

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