Who is Considered a “Junior” Horse?

When considering dietary requirements, junior horses are generally considered those that are under 2 years of age. After birth, most horses will continue to grow until they reach 5 years of age. For slower maturing horses, like draft breeds, growth may continue until they reach 7 years of age. However, when looking at daily nutritional requirements, a horse that is older than 2 years old has dietary needs similar to adult horses.

Junior horses’ daily nutrient requirements have been established by the National Research Council (NRC, 2007). Using research-based evidence, nutritionists have laid out specific daily requirements for growing horses beginning at 4 months of age, up until 24 months of age.

Baseline Dietary Requirements for a Horse

To give comparison to how nutrient requirements differ with junior horses, below are the requirements for an adult horse with little to no activity. This is assuming we are looking at a typical riding-type horse with a weight of 1100 pounds (500 kg) with no underlying health or metabolic issues. This demonstrates how much higher nutrient requirements are for our younger horses. More importantly, this demonstrates why many feeds designed for adult horses may not be appropriate for growing horses. This is because these feeds either do not meet a young horse’s daily dietary needs, or are imbalanced for young horses in some nutrients, such as calcium and phosphorus.

The basic minimum daily requirements of adult, non-working horses:

  • Protein (amino acids): 8% of feed
  • Mcal (megacalories): 16.7 total per day
  • Calcium: 20 grams per day
  • Phosphorus: 14 grams per day
  • Vitamin D: 3300 IU per day
  • Vitamin E: 500 IU per day  

What are the Nutrient Requirements for a Weanling?

Weanlings are young horses older than 3 months of age, but not yet 1-years old. Weaning is the process of transitioning the young horse from its mother’s milk to a diet of only eating solids (forage and feed). Most horses aren’t weaned from their mothers until at least 4 months of age, but often closer to 6 or 7 months of age. As a side note, creep feeding is used to help transition a suckling foal to a diet of forage and feed. You can learn more about creep feeding your foal HERE.

The first year of life for any foal is a time of dynamic growth. For most breeds, horses reach nearly 80% to 85% of their potential height in just their first year of life. Thus, their dietary requirements to support this growth are high when compared to the maintenance diet (low activity) for an adult horse.
Some of the basic minimum daily requirements at 4 months of age:

  • Protein (amino acids): 14.5% of feed
  • Energy in Mcal (megacalories): 13.3 total per day
  • Calcium: 39.1 grams per day
  • Phosphorus: 21.7 grams per day
  • Vitamin D: 3740 IU per day
  • Vitamin E: 337 IU per day

As the horse ages, these requirements shift. Some of the basic minimum daily requirements at 6 months of age until 1 year of age:

  • Protein (amino acids): 14.5% of feed
  • Energy in Mcal (megacalories): 15.5 total per day
  • Calcium: 38.6 grams per day
  • Phosphorus: 21.5 grams per day
  • Vitamin D: 4793 IU per day
  • Vitamin E: 337 IU per day

While the differences are minor between a horse from 4 months to a year of age, it does capture the higher requirements than those of an adult horse.

Important Consideration

It is also during this period with young horses that we become concerned with Developmental Orthopedic Disease/Disorder (DOD). Briefly, DOD may be linked to the improper nutrition of a growing horse. The latest research suggests diets high in carbohydrates (NSC), in addition to micronutrient imbalances, are contributing factors. Thus, owners need to carefully monitor their horses during this time. More about DOD and how it may be related to nutrition HERE.

What Are the Nutrient Requirements for A Yearling?

Yearlings are horses that are 1-years old and under 2-years old. The term “long yearling” is often used when a horse reaches 18 months of age (1.5 years old). While growth tends to slow for most horse breeds at this point, draft horses and similar breeds will continue to experience dramatic growth spurts.
Some of the basic minimum daily requirements at 12 months of age:

  • Protein (amino acids): 12.6% of feed
  • Energy in Mcal (megacalories): 18.8 total per day
  • Calcium: 37.7 grams per day
  • Phosphorus: 20.9 grams per day
  • Vitamin D: 5589 IU per day
  • Vitamin E: 642 IU per day

Some of the basic minimum daily requirements at 18 months of age:

  • Protein (amino acids): 11.3% of feed
  • Energy in Mcal (megacalories): 25.0 total per day
  • Calcium: 37.0 grams per day
  • Phosphorus: 20.6 grams per day
  • Vitamin D: 6161 IU per day
  • Vitamin E: 775 IU per day

When compared to weanlings, these values shift for yearlings to match their slowed growth, but remain enough to support increased activity and training.

Feeding the Junior Horse

The above cited values are used by equine nutritionists when formulating feeds and giving dietary recommendations to horse owners. When choosing what to feed your horse, there are many considerations, depending on breed and type of horse. However, certain guidelines can be applied to most junior horses.

  • Always feed high-quality forages (hay/pasture). Young horses need quality forage to ensure they are receiving adequate amounts of nutrients.
  • Select quality feeds based on the type and quality of forage fed. Because we want to avoid DOD, it is critical that only appropriate feeds are fed to young and growing horses.
  • Always follow manufacturers feeding instructions.

Other important feeding tips include:

  • Feed at least 2 times per day, though 3 to 4 times per day is even better for young horses.
  • Always provide free choice access to clean water.
  • Maintain young horses in an appropriate body condition (ideally a score of 5-6).
  • Weigh or use a weight tape every 2 to 4 weeks to make any necessary adjustments to their diet.

Conclusion
We understand it is challenging to feed young horses because of so many factors, such as the breed of the animal, its intended use, when it enters training, the type of training, and more. Thus, we would love to help you in designing a personalized feeding plan. Reach out today!

Chris Mortensen, Ph.D.