Care and training considerations

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This horse’s profile

MSTN TT

  • This horse has genetic markers indicating it will show energy efficiency over long distances.
  • This horse is genetically predisposed to enhanced performance in an activity that calls for long-duration, low-intensity exercise such as endurance.
  • Lower body weight to height ratio leading to a reduction of mechanical loading on the joints.
  • This horse lacks the explosive speed and rapid stride frequency required to perform competitively in sprints.

The three MSTN profiles of Anglo-Arabians:

Sprinter (CC genotype)

The CC sprinter genotype Anglo-Arabian possesses impressive strength that allows them to gallop with a compact stride to counterforce the impact of the ground underneath. This type of horse typically has a flatter profile while galloping, a lower head carriage and a shorter neck, which pushes significantly more weight onto the forelimbs to move the center of gravity forward. Sprinters are designed for short-distance running as their strong muscle fibers encourage a compact stride, which counterforces the impact of the ground underneath.

Middle-Distance (CT genotype)

The CT handy genotype of Anglo-Arabian may race like a sprinter or a stayer, but still can call upon traits from either type, which makes them highly versatile. They might have good reserves for acceleration, as if finding another gear at the end of a race, or they may be able to stay competitive over longer distances outracing long striders with a slow stride turnover, and outlasting short, striding explosive sprinters.

Endurance (TT genotype)

Anglo-Arabians with the TT endurance genotype are often built lighter, with longer limbs, sloping shoulders, lean hindquarters, and a slightly shallow girth that provides scope for extension and a long stride. The light upper body combats external forces such as weight and wind resistance, which increase over longer distances of more than 2200 meters. Compared to a stouter, more muscular rival, this type of Anglo-Arabian expends proportionally less total energy to gallop the same distance, resulting in less fatigue.

Training considerations

Lacking in early speed, this genotype’s strength lies in its ability to outpace rivals over a sustained distance. 

Anglo-Arabians of this genotype usually have a balanced stride frequency and lean conformation that allows their muscles to stretch fully (a bit like a rubber band being fully stretched to generate maximum power).

With a high proportion of flexible and fatigue-resistant type 1 muscle fibers, this horse is genetically suited to endurance racing and will achieve the most favorable result if trained and raced as a long-distance horse. The energy source is finer and though it does not necessarily provide the same explosive power, it is sustained and therefore ideal for long-distance racing.

Regular sprint work is critical to prevent horses in high-intensity sports from injury

A horse’s fast-twitch muscle ratio and bone density can be improved by alternating periods of lower effort performance (slower-paced) and higher effort (faster-paced) training.

The forelimbs absorb up to 65 percent of the weight-bearing impact while galloping, and this results in the lower limbs being prone to stress fractures and tendon and ligament injuries.

All horses lack muscles below the knee, and all movement in the lower leg area is carried out via tendons attached to the muscles higher up, so care should always be taken to correctly warm up and cool down a horse in training. Fatigued muscles are more likely to cause injury.

Too much circular training (including longeing) may cause uneven loading of the cartilage. It is better to train over straight lines of 50-100 meters. Introduce speed slowly, gradually upping the distance from just a couple of strides to sprints of 100 meters.

How to prevent stress fractures

This horse will benefit from early soft exposure to exercise, where bone remodeling occurs in response to the physical stress of training. This can help the bones and tendons become thicker and stronger, lessening the chance of injury later in life. Slow conditioning and daily sessions of short, straight sprints are also beneficial. 

If a young Anglo-Arabian horse is kept in a stable without access to turnout, or daily sprint training, it will lose bone mass and actually become weaker, not stronger.

A study by Michigan State University discovered a surprising side effect of early confinement of performance horses. Stalled horses suffered a marked decrease in bone mass and strength compared to horses kept on pasture, which was noticeable after just two weeks of stabling. While a stall-kept horse can gain good muscular strength because of training, underneath the shiny coat and muscles, the bones could be at their weakest.

Bones need to bend, and if the horse is not given the chance to ‘bend’ its bones (whether through training or outside during play), the body mechanisms of the horse will think the bones are already strong enough and try and get rid of extra minerals to provide more bend.

If the bone bends too much, such as when the horse is pushed to exert force on the bones through bursts of sprinting (either during training or at play), then its body does the opposite, presuming the bones are too weak and need to get stronger.

Bone transformations might not negatively affect performance for a recreational horse, but for an endurance horse, extended periods of stabling without proper exercise can contribute to injuries since the horse will certainly lose bone mass.

A word of caution

Injuries and breakdowns can easily occur when horses are pressured to perform too early or given an insufficient rest period after injury.

This horse has longer prime moving bones and leaner, more flexible muscles than other MSTN genotypes, meaning the fracture risk caused by larger muscle mass loading around the joints is reduced.

Anglo-Arabians of this genotype are, however, slower to mature than other MSTN genotypes. As this horse matures, the cartilage on either end of each bone will fuse, with the knees usually fusing between two and three. This makes the knee area vulnerable to injury if training is initiated too hard, too soon. Early injury may jeopardize the horse’s ability to run successfully in later years.