By Shelagh Niblock, PAS

You chose both the mare and the stallion, and you waited almost a year during the gestation of your anxiously anticipated foal. Now the foal is here and approaching the age to wean. The mare has done an admirable job of supporting that young life for the past 15 months during pregnancy and nursing, but now you must take over the task of meeting the nutritional requirements of your growing horse.

The successful feeding of young horses post-weaning demands that we meet their nutritional needs for maintenance as well as for growth and development, and as they get older there may be nutrients required for work.

Failure to meet the nutrient needs of growing horses can restrict their development and may affect their productivity later in life. Good nutritional guidelines for growing horses have been established in the National Research Council Nutrient Requirements of Horses (NRC), and there are plenty of manufactured supplements and feeds for growing horses available. So, feeding that young horse should be easy, right? Not always! Genetic factors, forage quality, and management are all significant contributors to the development of a successful feed ration for the growing horse. How do you get it right? 

A young horse with classic signs of nutrient deficiencies including a pot belly and poor hair coat. Photo: Canstock/ARTS

The Importance of Balance

Growth in young horses is multifaceted and consists of bone growth, development of soft tissues, and weight gain. A critical aspect of healthy growth in the young horse is skeletal development. Balanced nutrition is a fundamental aspect of healthy bone growth. Weight gain that is in excess of what the developing skeleton can support will cause problems. Rations for growing horses must be balanced for essential nutrients without providing excessive energy, and for all nutrients to permit good bone development without excessive weight gain.

What is a Limiting Nutrient?

Protein is an important nutrient, but even more important is protein quality. Protein is comprised of “building blocks” called amino acids. Some amino acids are in plentiful supply in equine diets, and some are not and so are called “essential amino acids” and must be supplied daily in the diets of growing horses. 

An example of an important essential amino acid in the diet of a growing horse is lysine. Lysine is a “limiting nutrient” in any equine diet that does not provide sufficient intake of it to support the growth requirement of the horse. In other words, equine diets where lysine is a limiting nutrient will permit only as much growth and development as the amount of lysine. The young horse may continue to gain weight if energy is in plentiful supply in the ration, but skeletal development may be hindered. This can cause slowed or stunted growth and excess body weight gain, a recipe for developmental orthopedic disease (DOD).

The same concept applies to other nutrients such as calcium, phosphorous, and trace minerals. Calcium and phosphorous are important for mineralizing the protein matrix in growing bone, but they must be present in both the sufficient amount and the correct ratio for successful growth. Trace minerals are an important part of the mineralization of growing bone and so dietary deficiencies or imbalances in copper, zinc, or selenium may result in any one of those minerals becoming a limiting nutrient. Rations for growing horses must have sufficient nutrients fed in the correct ratios to permit good bone development.

Foals accustomed to eating foal-starter prior to weaning usually handle the cessation of mare’s milk better and are less likely to go through a post-weaning slump in condition. Photo: Shutterstock/Lenkadan

Feed Intake 

Ensuring the youngster has sufficient nutrients for healthy growth means you must have some idea of their feed intake. A diet that contains a satisfactory nutrient profile for the growing horse must be consumed in sufficient quantities to deliver the nutrients required. This can be an area of particular concern in the choice of hay for your youngster. Because growing horses have smaller body size, if hay is of poorer quality, consumption may not be enough to meet nutrient demands. Course hay with low digestibility will often result in growing horses with classic signs of nutrient deficiencies including poor hair coat, poor immune function, and pot bellies. Good quality hay is always the foundation of a balanced ration for the growing horse.

The Weaned Foal 

The feed intake of a weaned foal is low due to small body size, small mouth, milk teeth, and limited capacity in the cecum or hindgut. At the same time, the growth rate of the weaned foal is very high and accordingly, the nutrient density of the weaned foal diet must be high. Weanlings must have access to quality hay or to pasture with high digestibility. They will also need balanced supplementation of important vitamins and minerals.

Ideally, foals should be started on a concentrate prior to weaning. Foals accustomed to eating concentrates like a good quality foal-starter pellet will be far less likely to experience a post-weaning slump in condition following the abrupt cessation of mare’s milk. Foals consuming at least a kilogram per day of 16 percent protein foal-starter are usually better equipped for weaning than foals consuming forage alone.

Quality hay, good pasture, and foal-starter pellets or balancer pellets fed accord to the bodyweight of the weaned foal can be continued until one year of age. Pay close attention to growth rates and bodyweight gain. Commercial foal starters may provide more energy than that required by large warmblood weanlings who can potentially consume larger quantities of quality forage. In this or similar circumstances, it may be necessary to reduce the foal-starter intake of your warmblood and initiate the feeding of a balancer pellet fed according to the manufacturer’s directions.

As noted above, attention must be paid to the amount of lysine the balancer pellet is providing. National Research Council Equine Nutrition Guidelines suggest that growing horses between the ages of four to ten months require approximately 180 milligrams of dietary lysine per kilogram of body weight of the foal per day. If you choose to feed a commercial balancer pellet, check the tag to ensure this requirement is being met. If the lysine content is not noted on the Guaranteed Analysis on the tag, call the manufacturer to ask what the content is and whether the balancer pellet is formulated for growing horses. 

Carefully monitor growth rate by taking lots of photos and keeping regular records of body weight. The growing horse needs a ration that delivers all essential nutrients without excessive energy and weight gain. Photo: Shutterstock/Nigel Baker Photography

The Yearling

Yearlings have a slower growth rate than weanlings and their feed intake is higher due to larger body capacity, so the nutrient density in the diet of the horse between one and two years of age needs to be lower. Key to the successful diet for a yearling is providing quality forage, as well as free choice salt, water, and a good vitamin and mineral supplement given according manufacturer’s directions.

Yearlings fed superior quality forage may do better on a diet that also includes a balancer pellet. Diets based on quality hay fed in combination with high nutrient density supplements such as balancer pellets are often a good choice for the slower growing, large breed horses.

Yearlings fed balanced rations with sufficient nutrients can look “framey” and still be on track for good growth and development. Remember, your goal is to allow your young horse to establish a skeleton of strong healthy bone that will withstand the rigours of a productive life. Yearlings can be slightly angular and gawky-looking without being thin. Practice body condition score (BCS) assessing skills with your yearling and get used to evaluating what sufficient (but not excessive) body condition looks like. 

Two Years and Older 

Growing horses at two years and older need the same attention to limiting nutrients as younger horses, but because they are larger with slower growth rates, quality forage becomes the feed of choice for them. They still need scrupulous attention to the risks associated with limiting nutrients, and therefore a good mineral must be provided at an intake as directed by the manufacturer. Pay attention to the amount of trace minerals such as copper, zinc, and selenium in the mineral you choose, as well as the amounts of fat soluble vitamins A, D, and E.

At this point in their lives, many two-year-old horses are beginning their training and will need to have nutrient requirements for work factored into their ration. Again, good hay ticks a lot of boxes for these horses, but if extra energy is needed, beet pulp, oats, or a manufactured concentrate can help. A diet of oats and grass hay for a growing horse may not meet protein needs, and if fed, a protein/mineral supplement of some sort will be required. When the energy requirements of a young horses increase, often the inclusion of some alfalfa hay cubes or pellets in the diet can provide safe supplemental energy.

Different breeds of horses are considered “mature” at different ages. Many of the lighter breeds of horses, such as Arabs, Quarter Horses, Thoroughbreds and pony breeds, are considered mature by the time they are about four to five years old. Large breed horses including draft and warmblood breeds, however, are not generally considered to be of mature size and weight until they are at least six to seven years old. Be sure to feed your five-year-old warmblood, who is now engaged in light but consistent work, like the growing horse he still is. 

Too Much Energy?

Many concentrates intended for the growing horse are high in starch and are energy dense, but they can be an important part of a good diet for the growing horse as long as it is a balanced ration. Good quality hay will deliver a lot of the key nutrients, but depending on the hay analysis it may be necessary to provide a protein supplement as well. Some commercial foal starters and growers provide an excellent source of essential nutrients, but intake is important. If the supplement has to be fed at a high level in order to provide sufficient essential nutrients, there is a risk that the growing horse will consume more energy than advisable. When feeding supplements containing starch, sugar, or fat, watch the BCS of your young horse very carefully. A good practice is to take regular pictures and record their body weight as determined by the use of a weight formula or weight tape. A photographic record of growth can be invaluable in making management decisions during growth and development.

Different breeds mature at different ages and feeding programs should factor in nutrient requirements for work once training begins. Although lighter breeds such as Arabians and Thoroughbreds are considered mature at four to five years of age, larger breed horses such as drafts and warmbloods are not at mature size and weight until they are at least six to seven years old. Photo: Shutterstock/Grigorita Ko

Developmental Orthopedic Disease

Rapid growth in young horses has been associated with an increased incidence of development issues arising from nutritional deficiencies. Developmental orthopedic disease can include epiphysitis, osteochondrosis (OCD), contracted tendons, angular limb deformities, and wobbler syndrome. There is abundant active research in the area of DOD in horses and no direct cause or effective cure has been established at this time. It is assumed that the incidence of developmental disease in young horses is multifaceted and can include genetics, the nutritional regimen of the growing horse, and possibly the nutritional regimen of the dam while she was pregnant and lactating. The best protection against DOD in your growing horse is a safe, balanced diet including quality forage and supplements to ensure there are no limiting nutrients. 

Pre-weaned and weaned foals should be allowed plenty of exercise, but with growing horses be cautious about initiating training too soon. Hard repetitive work too early in the career of a performance horse can result in excessive wear and tear on joints, ligaments, and developing bone. Keep the training to what is sufficient to establish a good working relationship with your young horse, but hold off on introducing harder work until later in development.

What is Compensatory Growth?

Young horses who have experienced growth setbacks either due to disease, management, or nutritional shortfalls are at risk of a condition called “compensatory growth” should they suddenly be started on a diet with more nutrient density. Compensatory growth occurs when the young horse’s body is trying to “catch up” and fulfil its genetic potential. Unfortunately, the rapid growth that occurs under conditions of compensatory growth is frequently unsound and it may contribute to the incidence of DOD. If you acquire a youngster who may have had a rough start in life, reintroduce a healthy diet gradually. Slow steady growth is always the best.

Young horses who have gained too much weight and need to have their energy intake reduced must never be put on a starvation diet. A gradual reduction in energy intake will generally allow the young horse to grow into his excess body condition. When managing the diet of a young horse who needs to slow down his growth rate, ensure that all potentially limiting nutrient needs are always being met.

For the growing horse, good quality hay is always the foundation of a balanced diet. Smaller weanlings are not able to manage as well on forage alone due to their lower feed intake. Photo: Shutterstock/Victoria Rak

Guidelines for Feeding Growing Horses

• Body size is important. Bigger weanlings can eat more forage. Smaller weanlings can’t manage as well on forage alone. Feed intake should be monitored especially in “at risk” growing horses.
• Always choose quality forage for the growing horse. That doesn’t have to mean the highest protein hay, but it does mean hay that is vegetative, nutritious, and easy to eat with a smaller mouth.
• Ensure that the diet you put together for your growing horse is balanced with no risk of limiting nutrients. Good hay and pasture fed in combination with a good commercial supplement can be an excellent way to accomplish this.
• Remember to include parasite control in your equine management routine. Speak to your veterinarian about an effective deworming protocol for growing horses in your area.
• As much as possible, manage your young horse to minimize stress and ensure his environment is conducive to healthy growth. Safe barns with good ventilation, good fencing, and turnout where possible are all part of optimum management for the growing horse. 
• Pay attention to growth rate. Take regular photos and keep records of body weight. If signs of DOD develop, contact your veterinarian immediately.  

Remember that feed quality, management, and genetics have a significant impact on the progress of any growing horse. If you have concerns, speak to a qualified equine nutritionist or your veterinarian right away.

Enjoy the experience of watching your young horse grow up and the anticipation of a bright future together. 

Main article photo: Shutterstock/Grigorita Ko

This article was originally published in the Autumn 2019 issue of Canadian Horse Journal.