A balanced feeding program is key for yearling horses, as it sets the foundation for their growth and development into adulthood. Yearlings are transitioning from foals to young horses, and their nutritional needs are unique during this stage of life.

Yearlings require higher energy and protein levels compared to mature horses to support healthy growth and muscle development. They also need a balanced intake of essential vitamins and minerals, like calcium and phosphorus, for sound bone development.

The best way to meet these needs is with good quality forage and appropriate supplementation. Adding alfalfa hay and/or soybean meal is often sufficient to meet the increased protein needs of yearlings. Feeding a balanced vitamin and mineral supplement can also help to avoid nutrient deficiencies that can impair growth.

For additional support, you can consult with an equine nutritionist to ensure your horse’s diet is well-balanced. Working with a qualified nutrition is especially important if you plan to develop your yearling for athletic disciplines, helping to set them up for success in the performance arena.

Growth in Yearling Horses

Horses between the ages of 12 and 23 months old are called ‘yearlings’, and those that are 18 months and older are often referred to as ‘long yearlings’.

During this stage of life, yearlings undergo rapid growth, with noticeable changes in height and body proportions. Regularly monitoring your yearling’s growth rate is critical for supporting their overall health and future performance goals.

Growing too slow can result in failure to achieve their optimal mature size, whereas growing too fast increases the risk of developmental orthopedic diseases and joint issues in later life. [2]

Yearlings typically reach 65% of their mature weight by one year old, and 80% of their mature weight by 18 months old. [2] For a growing horse that is expected to reach a mature weight of 1,100 lbs (500 kg), this equates to:

  • 12 months old: 715 lbs (325 kg)
  • 18 months old: 880 lbs (400 kg)

Consider the breed of the yearling’s sire and dam to estimate their mature weight.

Growth Rate

Your yearling’s growth rate depends largely on their genetics, feeding program, and level of exercise. [2] Foals grow most rapidly during the first few months of life, and their growth rate slows down towards their yearling year and beyond.

This is not a linear decline, but resembles a wave pattern that is influenced by external factors such as: [2]

  • Length of Day
  • Temperature
  • Forage availability

Smooth Growth Rate

The goal of feeding programs for yearlings is to achieve a smooth rate of gain throughout the growth phase. Periods of suboptimal nutrition can temporarily slow down the growth rate due to nutrient restriction.

When nutrition is improved, periods of more rapid growth can follow, known as compensatory gain. [2] While compensatory growth can effectively get a horse caught up in terms of overall body size and weight, it may not result in uniform skeletal development. This can lead to orthopedic issues, including developmental orthopedic diseases (DOD).

When formulating diets for yearlings, we aim to avoid or minimize compensatory gain to promote long-term soundness. This can be accomplished by adjusting the diet in response to forage quality and availability to provide consistent nutrition.

Average Daily Gain (ADG) for Yearling Horses

Mature Weight 12 Months Old 18 Months Old
400 kg (880 lb) 0.36 kg (0.79 lb) 0.23 kg (0.51 lb)
500 kg (1100 lb) 0.45 kg (1 lb) 0.29 kg (0.64 lb)
600 kg (1320 lb) 0.54 kg (1.2 lb) 0.34 kg (0.75 lb)

 

Average Daily Gain Calculator

Enter your horse’s predicted mature weight and their current age in months below to calculate their expected Average Daily Gain (ADG).

Calculate Average Daily Gain (ADG)



Results:

Average Daily Gain:

 

This calculator estimates your yearling’s average daily gain using the following equation, where M is the predicted mature body weight (kg) and A is the yearling’s age in months: [3]

ADG (kg) = M x 6.97 x (e(-0.0772xA))/3040

Monitoring Growth

To effectively monitor your horse’s growth rate, you can use the following measures:

  • Body weight
  • Wither height
  • Hip height
  • Body length
  • Heart girth

At a minimum, body weight and wither height should be regularly measured using a scale and weight tape. Record these measures over time to inform feeding decisions, particularly in situations where growth rate needs to be limited or increased.

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7 Steps to Feeding a Yearling Horse

Feeding a yearling horse between the ages of 12 to 18 months requires careful attention and management to support their growth and health.

By one year of age, a yearling’s gut is mature and can readily process forages. [1] The best way to support your yearling is to provide a balanced, forage-based diet, mostly composed of hay and pasture. Additional supplementation is required to meet vitamin and mineral needs, but grain-based feeds should be avoided as they can contribute to gut issues and metabolic problems.

This guide provides a practical, step-by-step approach to ensure your yearling receives the right nutrition and care for a strong start in life.

1) Assess Body Condition

Whenever making changes to your horse’s feeding program, start by assessing their body condition to determine whether they are at a healthy weight. Along with monitoring growth, you should regularly track your yearling’s body condition score.

Proper body condition scoring involves visually assessing and palpating (touching) six key areas to assign a numerical score to the fat cover.
Inspect your horse visually from the front, back, and sides looking for areas that are noticeably thin or thick. If your yearling allows, palpate the following locations:

  • Neck
  • Withers
  • Loin
  • Ribs
  • Shoulder
  • Tail head

Score your horse between 1 (emaciated) to 9 (very obese), taking into account the fat accumulation at each of those six areas. The body condition of a yearling should fall between 4 and 6 on the 9-point Henneke body condition scale. [2]

Maintain a log of their score and track changes over time so you can make any adjustments to the diet, ensuring your yearling remains in optimal condition.

2) Estimate Nutrition Requirements

Compared to mature horses, yearlings have higher relative energy, protein, vitamin, and mineral requirements based on their body weight. The additional nutrients they consume are important to enable healthy growth of bone, muscle, and vital organs.

Energy

The energy requirements of growing horses are the sum of:

  • Energy needed to maintain their current condition
  • Energy needed to gain weight at the appropriate rate
  • Energy needed to fuel exercise for those beginning training programs

To estimate this, we use their current body weight, average daily weight gain, age in months, and their activity level. [3]

Protein

Protein is an important part of yearling diets, as it is used to support growth of muscle and other tissues. In addition, yearlings are estimated to require more protein to maintain their current body mass than mature horses. [4]

For long yearlings that are beginning a training program, requirements will also be elevated to meet the demands of performance.

Daily Requirements for Yearling Horses with a Predicted Mature Weight of 500 kg (1100 lbs)

Nutrient 12 month old 18 month old
Energy 22.5 mcal 23.1 mcal
Protein 1015 g 959 g
Lysine 44 g 41 g
Calcium 45 g 44 g
Phosphorus 25 g 25 g
Zinc 386 mg 465 mg
Copper 96 mg 116 mg

 

3) Feed a Forage-First Diet

Forage should provide the foundation of your yearling’s diet. Adequate forage intake supports gut health in horses and enables expression of natural grazing behaviors.

Pasture is an ideal forage source for yearlings, as it combines abundant protein and energy with the opportunity to move and socialize freely. If pasture is not available, high-quality hay is a good alternative.

Choosing Hay for your Yearling

While some visual cues, like soft hay with lots of leaf, can indicate high quality hay, appearance is not always a good predictor of the nutritional value of forage. [5]

To determine whether your hay will meet your yearling’s needs, a forage analysis is strongly recommended. A forage report will tell you the energy, protein, fibre, carbohydrate, and minerals levels in your hay.

In general, hay that is harvested at a mature growth stage will have higher fibre and lower protein and energy content. Conversely, early growth hay will provide more protein and energy, and be less fibrous.

For most yearlings, an early-maturity grass hay or mixed grass/alfalfa hay will come close to meeting their protein and energy needs. If possible, analyze each batch of hay to accurately balance your yearling’s diet for optimal growth.

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Forage Intake

Growing horses consume approximately 2.5% of their body weight per day in dry matter. An average 880 lb (400 kg) yearling may consume as much as 24 lb (11 kg) of hay per day, depending on the the rest of their diet.

As yearlings get older, their nutrient requirements decrease relative to their body weight, meaning that less supplemental energy and protein are required. Once they reach maturity, forage can make up a greater proportion of the horse’s diet.

4) Meet Energy Demands

Your yearling’s diet needs to meet their energy requirement without significantly exceeding them to ensure healthy growth and development. Excessive energy intake can cause rapid growth, which may predispose growing horses to developmental orthopedic diseases. [6]

Typical yearlings need to consume 22.5 megacalories (mcal) of energy per day, while long yearlings need 23.1 mcal a day. [3]

When choosing energy sources, aim for feeds that are low in hydrolyzable carbohydrates (HC). These are the non-structural carbohydrate fractions, namely starch and simple sugars, that are easily digested in the small intestine and contribute to insulin release. High intake of starch and sugars can impact gut health, interfering with nutrient absorption and growth of the horse.

Suitable energy sources for yearlings include:

When feeding alfalfa or bran, careful attention must be paid to the ratio of calcium to phosphorus in the overall diet. Alfalfa is high in calcium whereas brans are high in phosphorus.

Feeding alfalfa alongside wheat bran or unfortified rice bran can help to keep the calcium to phosphorus ratio in check while meeting energy needs.

5) Meet Protein Requirements

High-quality protein is an important part of a growing horse’s diet. A high-quality protein is one that provides essential amino acids that the horse’s body cannot make on its own. If these amino acids are not adequately supplied in the diet, the horse’s ability to make proteins and build their muscles and other tissues can become limited.

The average 715 lbs (325 kg) yearling requires 846 grams of protein per day. [4] Seeds such as alfalfa and soybean meal are palatable protein sources that you can use to supplement the diet. If your yearling requires both supplemental energy and protein, consider feeding roasted soybeans which are high in protein and contain fats for energy.

By 18 months of age, protein demands begin to decrease. The average 880 lbs (400 kg) long yearling needs to consume 799 g of protein per day. At this stage of growth, high-quality hay may be sufficient to meet protein requirements.

If you are feeding a lower-quality hay, amino acids can be supplemented in addition to a high-protein feed to improve the overall protein quality of the diet.

Mad Barn’s Three Amigos is a pure amino acid supplement that provides lysine, threonine, and methionine – the three amino acids that are most likely to be deficient in a growing horse’s diet.

Three Amigos

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  • Optimal protein synthesis
  • Hoof & coat quality
  • Topline development
  • Athletic performance

6) Meet Vitamin and Mineral Needs

Vitamins and minerals are essential nutrients for healthy growth and development of yearling horses. As your yearling grows, their vitamin and mineral requirements increase as well.

Calcium and Phosphorus

Calcium and phosphorus are two minerals that are important for proper bone growth and strength, comprising 52% of a horse’s bone tissue. [7] These minerals are also involved in various physiological processes, including nerve function, muscle contraction and cellular communication.

Yearlings need adequate calcium and phosphorus in their diet to support skeletal health and overall development. The ratio of calcium to phosphorus in the diet must also be maintained between 1:1 to 3:1 to ensure proper calcium absorption.

Magnesium

Magnesium is a significant component of the skeleton, and also plays an important role in muscle contraction. [8] Low magnesium intake in horses can lead to: [8]

  • Nervousness
  • Muscle tremors
  • Ataxia

Forage, especially legumes like alfalfa are a rich source of magnesium. Average-quality grass hay will also typically meet the magnesium requirement of yearling horses.

Sodium

Sodium is an electrolyte nutrient involved in maintaining acid-base balance and facilitating nutrient transport into and out of cells of the body. [8] Low sodium intake in horses can lead to several issues, including : [8]

In some areas of the midwestern United States, forage is a good source of sodium. However, in most areas forage is a poor source of sodium.

You can meet your yearling’s sodium requirements by adding loose salt to their meals, as well as providing a source of free-choice loose salt.

Copper

Copper is a trace mineral that is involved in the production and maintenance of connective tissue. It also plays diverse roles such as mobilizing iron stores, supporting mitochondria, and aiding in antioxidant defenses. [8]

Low copper intake in horses can lead to conditions including: [8]

The copper content of most forages is quite low and will typically not meet requirements for yearlings. It’s important to feed a source of supplemental copper to ensure your yearling’s needs are met.

Zinc

Zinc is another trace mineral that is involved in a wide array of functions in the horse’s body. [8] Low zinc intake may lead to: [8]

Like copper, the zinc content of forages is often quite low and will not usually meet yearlings’ requirements. Supplementation with zinc is typically necessary for all horses.

Selenium

Selenium is an important component of antioxidant systems, and also plays a role in the immune system and regulating thyroid hormone metabolism. [8]

Selenium deficiency in horses causes muscle issues that are characterized by: [8]

  • Weakness
  • Impaired locomotion
  • Difficulty swallowing
  • Respiratory distress

The selenium content of some forages grown in the midwestern United States will meet yearlings’ needs. However, for the majority of the United States and Canada, selenium content of forages is quite low. Feeding a well-balanced vitamin and mineral supplement can help to meet the selenium needs of horses in areas where forage supply falls short.

Trace Minerals

When supplementing trace minerals in your horse’s diet, nutritionists recommend providing them in chelated or organic forms that are more effectively absorbed from the gut and utilized in the body.

Mad Barn’s Omneity is a vitamin and mineral supplement for horses formulated to balance the majority of forages in North America. Omneity provides 100% organic trace minerals, including copper, zinc and selenium, to meet the needs of growing and mature horses.

Omneity – Premix

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  • 100% organic trace minerals
  • Complete B-vitamin fortification
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  • Our best-selling equine vitamin

Vitamin A

Vitamin A is another nutrient required in the equine diet that is important for night vision and the immune system. Vitamin A deficiency in young horses is associated with impaired growth and blood cell production. [9]

Hay can have varying levels of vitamin A, and beta-carotene, which the body converts into vitamin A, is often not measured in hay analyses. For this reason, it is recommended to provide yearlings with a supplemental source of vitamin A to ensure requirements are met.

Vitamin D

Vitamin D is a nutrient that is involved in bone health, tissue repair, immune function and calcium and phosphorus metabolism. It helps to regulate bone synthesis and breakdown, influencing calcium concentrations in the blood. [9]

Horses can get Vitamin D from their diet or synthesize it in their skin with exposure to sunlight. However, the dietary consumption of vitamin D2 appears to be the most important source of this nutrient for horses. [10]

Vitamin D deficiency can result in rickets, a condition that is characterized by bone deformities. While this condition has been observed in other mammals, it has not been reported in horses. However, without access to sunlight or adequate vitamin D supplementation, growing horses do experience impaired bone growth and development.

The vitamin D content of hay can vary, and like vitamin A, it is not commonly measured in forage analyses. Feeding supplements that contain added vitamin D ensures that your yearling’s intake is adequate.

Vitamin E

Vitamin E is an important antioxidant nutrient that helps to protect cells against oxidative damage. [9] It is also involved in neurological health, the immune system and muscle repair following exercise.

Deficiencies in vitamin E can result in conditions including white muscle disease and equine degenerative myoencephalopathy. [9]

The vitamin E content in grass declines after it is cut and stored to make hay, meaning that horses on a hay-only diet need supplementation to avoid deficiency. Fresh pasture is a good source of vitamin E, but often does not meet the needs of growing horses.

Choose a supplement that provides natural Vitamin E, which is better absorbed and utilized in the horse’s body compared to synthetic forms.

Vitamin E

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  • Optimal antioxidant protection
  • Supports exercise recovery
  • Supports immune function
  • Natural with high bioavailability

7) Provide Free Access to Water

Like all horses, yearlings should have free access to clean water in their environment at all times. Adequate water intake is important for many physiological processes, as well as for colic prevention and maintaining gut motility.

Monitor your yearling’s water consumption to ensure they are adequately hydrated. If you suspect your yearling is not consuming enough water, you can perform a skin tent test to check for signs of dehydration. If you suspect your horse is dehydrated, contact your veterinarian.

Adding 1 – 2 tablespoons of plain loose salt to your yearling’s daily ration can also encourage them to drink more water. For yearlings that are exercising, additional salt or electrolyte supplements may be needed to replenish the electrolytes lost in sweat.

Example Diets

Below are example diets for short and long yearling horses with an expected mature body weight of 500 kg (1100 lbs). These diets are based on the needs of typical horses and may not reflect your feeding situation or forage availability.

For personalized help deciding what to feed your yearling, submit their diet online for a free consultation with our qualified equine nutritionists.

Sample Diets for a 12- and 18-month old Yearling

Nutrient 12-months old 18-months old
Feed
Grass Hay Free-choice Free-choice
Alfalfa Hay 2.75 kg / 6 lbs
Alfalfa Pellets 0.9 kg / 2 lbs 0.9 kg / 2 lbs
Wheat Bran 0.45 kg / 1 lb
W-3 Oil 60 mL / 2 oz 60 mL / 2 oz
Omneity Pellets 175 g
(1.75 scoops)
200 g
(2 scoops)
Salt 15 g
(1 tbsp)
15 g
(1 tbsp)
Nutrient Analysis
Digestible Energy
(% of requirement)
92% 100%
Crude Protein
(% of requirement)
146% 162%
Lysine
(% of requirement)
151% 162%
HC
(ESC + starch; % of diet)
10.2% 8.9%
Fat
(% of diet)
3.4% 3.3%

 

In the example yearling diet, the digestible energy is intentionally undersupplied to maintain a lean body type and a slower rate of growth. Your nutritionist may recommend this feeding strategy to reduce the risk of developmental orthopedic diseases.

If you notice your yearling becoming too lean, you can increase the energy density of these diets by feeding more oil. Gradually increase the feeding rate over a few days up to 200 mL (7 oz).

Summary

  • Proper nutrition is important for yearling horses to maintain a smooth growth rate and support healthy skeletal development.
  • Regularly monitor the growth and body condition of yearling horses to make necessary dietary adjustments.
  • Ensure that your horse’s diet is well-balanced and meets energy, protein, vitamin, and mineral requirements.
  • Feed high-quality forage as the foundation of your yearling’s diet. A forage-based diet supports digestive health and mimics natural grazing behaviors.
  • Depending on the quality of the hay you are feeding, you may need to supplement energy and protein. Getting a forage analysis can help you determine hay quality.

Not sure if your yearling’s diet is meeting all of their needs? Submit their information online for a free consultation with our expert equine nutritionists to formulate an optimal diet plan.

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References

  1. Smyth, G.B. Effects of age, sex, and post mortem interval on intestinal lengths of horses during development. Equine Veterinary Journal. 1988.
  2. Remillard, R.L. et al. Chapter 21: Feeding Growing Horses. Equine Clinical Nutrition. 2023.
  3. National Research Council Chapter 1: Energy. Nutrient Requirements of Horses. 2007.
  4. National Research Council Chapter 4: Proteins and Amino Acids. Nutrient Requirements of Horses. 2007.
  5. National Research Council Chapter 8: Feeds and Feed Processing. Nutrient Requirements of Horses. 2007.
  6. Lepeule, J., et. al. Association of growth, feeding practices and exercise conditions with the prevalence of Developmental Orthopaedic Disease in limbs of French foals at weaning. Preventitive Veterinary Medicine. 2009.View Summary
  7. El Shorafa, W.M., et. al. Horse Metacarpal Bone: Age, Ash Content, Cortical Area and Failure Stress Interrelationships. Journal of Animal Science. 1979.
  8. National Research Council Chapter 5:Minerals. Nutrient Requirements of Horses. 2007.
  9. National Research Council Chapter 6:Vitamins. Nutrient Requirements of Horses. 2007.
  10. Dosi, M.C.M.C., et.al. The effect of season, management and endocrinopathies on vitamin D status in horses. Equine Veterinary Journal. 2022. View Summary