A lifelong love of horses often translates to a lifetime commitment, with many owners keeping their horses through several life stages. This article aims to summarize some key nutritional considerations for these stages, from point of conception to old age. It is, however, advisable to work with a qualified equine nutritionist to ensure your horse’s diet meets his nutrient requirements throughout his life.
NUTRIENT REQUIREMENTS GLOSSARY
Horses need several key nutrients: water, energy (from carbohydrates, fat and, to some degree, protein), amino acids (from protein), minerals and vitamins.
With respect to water, horses should always have free access to water, with adequate intake being particularly important for horses that are lactating or in work. The general minimum daily amount required is five litres for every 100kg of body weight.
Energy is measured in megacalories (equal to 1,000 x the kilocalories that human food is measured in) and is produced through the metabolism of carbohydrates including fibre found in forages like hay and pasture plus starches and sugars found in cereal grains, as well as fats and protein.
Protein is not a very efficient source of energy, but rather provides the amino acids that are required for tissue and compound synthesis within the body (like structural tissues such as muscle, or compounds such as hormones). Good sources of protein include soybean meal (or other seed meals) and legume plants (like alfalfa).
Major (macro) minerals such as calcium (Ca) and phosphorus (P) play a large role in metabolism, while the electrolytes – sodium (Na), potassium (K) and chloride (Cl) – are important for maintaining hydration status and electrical balance within the cell. The minor (micro) minerals include, for example, copper (Cu) and zinc (Zn) that are important for connective tissue and collagen synthesis, iron (Fe) that helps carry oxygen within red blood cells, iodine (I) that is required for thyroid hormone synthesis and selenium (Se) that functions as an antioxidant within cells. Minerals are found in a variety of forages and grains in varying amounts.
The fat-soluble vitamins (A, D, E and K) and the water-soluble vitamins (C) and the B-complex of vitamins (including niacin, riboflavin, biotin, etc.) assist with many biological reactions within the body. Horses don’t technically require vitamin C because they can synthesize their own, unlike humans, primates and fruit bats. Further, vitamin K and the B-complex of vitamins can be synthesized by the microbial organisms found within the horse’s digestive tract, such that it is very difficult to induce a deficiency in these vitamins. Vitamin D is the “sunshine” vitamin, in that it can be produced from sun exposure on the skin of the horse, and is also found within sun-cured hay. Vitamins A and E are found in excellent amounts in fresh forages such as pasture. The amounts of these nutrients required by horses are outlined in detail within the National Research Council’s (NRC) Nutrient Requirements of Horses (2007).
GENERAL FEEDING GUIDELINES
In terms of general feeding guidelines, horses evolved to graze, and have a digestive tract very suited to breaking down the fibrous compounds found in pasture and hay. Providing ample forage to mature horses can satisfy many (if not almost all) of the horse’s nutrient requirements, supply ample fibre to keep their digestive tract healthy and ward off gastric issues such as colic. It also allows the horse to spend his time grazing, as he would in the wild.
A rule of thumb, therefore, is to provide mature horses at least 1% of their body weight as (dry) forage per day – such that a 500kg horse should receive at least 5kg of dry hay, or, assuming pasture is at least 55% moisture, about 11kg of fresh pasture. Most horses will consume much more than that 1% if given free choice hay or pasture, averaging about 2-3% of their body weight in dry food intake per day. Growing horses that do not have a fully developed digestive tract, will not likely consume 1% of their body weight of forage, but instead meet their nutrient needs through milk, and eventually some forage and concentrate.
While forage (and water) can provide for most of a horse’s nutrient requirements, some horses may need to be supplemented with additional energy, protein, minerals or vitamins.
In terms of monitoring your horse’s nutritional health, simple tools such as monitoring body condition score, body weight (through estimation using a heart girth measurement) and height can tell you much about how your horse is doing, as can evaluating his overall health, performance and attitude.
Body condition scoring is a useful tool for owners of mature horses to monitor their horse’s fat coverage, and, therefore, his overall plane of nutrition. Using a scale developed by Dr. Don Henneke, horses are assigned a score from one to nine based on their fat coverage, with a horse that is a one being emaciated, and horse that is a nine being grossly obese. Ideally, most mature horses would be in the four (some ribs showing but otherwise healthy) to a six (some coverage, but not overweight) on the scale.
Horses at maintenance should be fed to maintain this ideal body condition, with adjustments made to the diet if the horse is too thin or too overweight, as significant health concerns can occur with either scenario. Should a horse vary too much in its body condition, a nutritionist can help evaluate the diet to modify energy intake, while not affecting the intakes of other nutrients. Similarly, monitoring body weight and height can be very important as a young horse develops, to ensure he is growing at a smooth and steady rate.
Other tools to assess nutritional status include having a full nutritional evaluation conducted on the diet, including hay or pasture analysis, to see what nutrients may be in excess or lacking for your horse. Unfortunately, bloodwork, urinalysis and hair analysis do not do a very good job in analyzing a horse’s nutritional status.
NUTRITION FOR LIFE
So, let’s start at the beginning. At conception and throughout fetal development, nutrients are provided through maternal nutrition. During the early stages of pregnancy, most nutrients are directed towards the development of the placenta, with the majority of growth of the fetus occurring within the last three to four months of pregnancy.
In general, the mare will utilize her own nutrient reserves to supply the fetus, such that minor deficiencies or excesses in the mare’s diet do not tend to negatively harm the foal. It is important, however, to feed the mare adequately, particularly towards the end of pregnancy so that her own body weight or nutrient reserves are maintained. Typically, a mare will increase her feed intake to meet these higher demands. Towards the end of pregnancy though, the large fetus pressing on the digestive system may make consuming large amounts of food difficult. This is why it may become important to feed concentrated nutrient sources to broodmares towards the end of pregnancy. Commercial feeds formulated for broodmares should provide all of the nutrients required by the mare and her growing fetus when fed in adequate amounts along with high-quality forages.
After birth, the mare will continue to play a key role in the foal’s nutrition and overall health, through her production of colostrum and milk. Ensuring adequate passive transfer of antibodies from the mare to her foal via colostrum is vital, as is ensuring her milk production is sufficient to meet the needs of the foal.
Unlike in humans, antibodies do not transfer through the placenta, and, therefore, the only source of antibodies for a newborn foal is through the consumption of colostrum. Peak milk production will occur approximately one month after birth, with production amounts decreasing over time until weaning.
Throughout lactation, it is vital to provide sufficient nutrients to the mare so that she transfers those nutrients into her milk. While feeding a good quality commercially formulated broodmare ration will help provide these nutrients, adequate provision of high-quality forage is equally important.
Eventually, the foal will begin to nibble on both of these feeds and a smooth transition from creep feeding to weaning can help minimize the stress of weaning by preparing the foal to begin eating entirely on his own. Similarly, as the mare’s milk production starts to decrease, there is an increased reliance for the foal to obtain more and more of his nutrients through feed.
Throughout weaning and the foal’s first year, there is a rapid rate of growth, and this can increase the risk in developmental orthopedic diseases (DODs) such as physitis or osteochondritis dessicans. DODs can result from deficiency in some nutrients (such as copper), or be influenced by genetics. It is, however, most often a result of a combination of high-energy (calorie) intake and rapid growth rate. Careful feeding of hay and concentrates, along with weekly monitoring of growth rate can help minimize the risk of DODs.
Ideally, the growth rate is smooth, without major growth spurts and lags. Because of rapid skeletal development during this time, the nutrient composition of the overall diet should be evaluated carefully to ensure there are adequate amounts of protein (and in particular the amino acid lysine), Ca, P, magnesium (Mg), Cu and Zn. Typically, a diet of good quality forages (including some legumes such as alfalfa) and a growing horse feed fed in moderate amounts to reach a slow and steady rate of growth will be ideal for such horses.
As the horse matures further, the growth rate will slow and most horses reach their mature height and weight by five years of age. Throughout this latter-growth stage, a young horse may be introduced to exercise training and work. To meet the needs for additional work and exercise, additional calories need to be provided in the diet, along with smaller increases in protein intake. In a younger horse that is also beginning to work, Ca and P intake are especially important as bone development and remodeling occurs with exercise.
Once the growth plates close and growing stops, the horse may be used for a variety of purposes in different sports and disciplines – or he may simply be a pet living in a field. Mature horses are designated to be at “maintenance,” “work,” or some state of breeding with reference to their nutritional requirements. Much of their nutrient requirements are, therefore, based on how much productivity (work or breeding) they have.
Horses that are at maintenance are those that are not growing, working or used for breeding – and their nutrient requirements simply meet demands for normal metabolism (breathing, heart beating, brain function) and minimal movements (such as from the waterer to pasture and back, swatting flies, mutual grooming, etc.). They should also be in a state of consistent body weight and condition (not gaining or losing weight) and are considered to be in a thermoneutral environment (meaning it is not so cold that they increase their metabolic rate to stay warm).
We must, however, recognize that even at maintenance, not all horses are the same, with some horses (or breeds) tending to have a slower metabolism and being “easy keepers,” while others are more difficult to keep weight on and are considered “hard keepers.” These horses, therefore, have different energy requirements and nutritionally would be considered “low maintenance” (for the easy keepers) and “high maintenance” for the hard keepers, compared to the average horse according to the NRC.
Horses at maintenance have relatively low requirements (even those harder keepers), and can be maintained fairly easily on decent quality forages (particularly pasture), some vitamin or mineral supplementation (based on the quality of the forages) and water.
Horses that are in work are classified by the NRC are as light work, moderate work, heavy work or intense work.
The light work category would represent horses that participate in recreation programs or are being introduced to training, and working one to three hours a week at the walk, trot and canter.
The moderate work category includes horses that would be found in riding schools and recreational programs, horses competing a horse shows, conducting some ranch work, or a horse working through breaking and training ,and working three to five hours per week at the walk, trot, canter, with some jumping or skills work.
A horse at heavy work would work four to five hours per week, with mostly trotting, cantering and galloping, along with jumping or skills work, such as heavier working ranch horses, horses competing in polo, show jumping, or low-level eventing and race training.
The intense work category would include racing horses, endurance horses and top-level eventing horses.
The nutrients required by these different classes of working horses will increase with work effort, with the largest increases seen in energy (calories) and water requirements, with other increases in Na, Cl and K (because these are lost in sweat), protein requirements (because nitrogen found in protein can also be lost in sweat, and to help support muscle growth and development), and other minerals and vitamins.
While horses are in their middle age (five to 15 or 20 years), their uses and productivity levels may change at various times, resulting in different nutrient demands and, ultimately, different feeding protocols.
Body condition can also be used to identify energy balance in athletic horses, though there do tend to be some differences between disciplines. Endurance horses, for example, tend to be very lean (about a three out of nine on the Henneke scale), while show jumpers and eventers and skill types of horses tend to be more in the four to five range and dressage horses and hunters being a little higher still. Racehorses, many of which are still actually growing, are typically very lean, with scores of around four out of nine. Little information is available regarding what body condition is “ideal” for different types of athletic horses. Nonetheless, if your horse loses weight during a competition season it is likely he needs more energy (calories) to maintain weight.
Typically, horses in light or even moderate work can meet their needs through increased intakes of forage, with perhaps a small amount of concentrated calories to fulfill any gaps. As horses move into higher degrees of work, concentrated energy sources, particularly those high in fat, will provide the calories required to perform. Because working horses consume, in general, more food, they do not necessarily need higher concentrations of nutrients such as protein. A horse consuming 3kg of a 10% protein feed per day, for example, would be consuming 300g of protein, and if that horse went into more work and started to eat 5kg of that same 10% protein feed to meet increased calorie requirements, he would now be consuming 500g of protein (in additional to all of the protein found in the forage).
Injuries or lameness that require stall rest or time off work will affect the working horse’s nutrient requirements and the feeding program should be adjusted accordingly.
As horses age into their senior years, there are changes to their dentition, digestive health and metabolism that may affect their nutritional status. The age in which a horse is considered “senior” varies (between 15 and 20 years), and is mostly determined by the quality of the horse’s teeth.
While there is little research to show that nutrient requirements truly change with age, there is some data to show that older horses have a reduced ability to digest protein, phosphorus and fibre, and it appears that they have a diminished capacity to produce vitamin C. Diets formulated for older horses, therefore, tend to be higher in protein and phosphorus, are high in easily digested fibre sources (such as beet pulp), and have added vitamin C (ascorbic acid). Such diets are often highly palatable and easily chewed by older horses that may lack teeth or have reduced grinding surfaces.
Monitoring body condition and having regular dental check-ups are essential for keeping older horses healthy. Owners of older horses can also make simple changes to feeding management to help out, such as feeding the old guys alone so they don’t have competition from other younger horses, soaking feed so it can be chewed more easily, and blanketing them in the winter to the minimize energy required to keep warm.
In summary, good quality forage and free access to water are the forefront of any nutritional program for your horse, with additional nutrients being met as needed through concentrated sources of energy, protein, minerals and vitamins.
Commercially manufactured feeds are designed to be nutritionally balanced for the class of horse they are intended for, and, therefore, take some of the guesswork out of feeding your horses. Owners may, however, prefer a more streamlined or tailored diet to meet their horse’s needs.
Keeping in mind the nutritional changes that may occur with your horse as they progress though stages of growth, breeding, performance and retirement can help your horses live healthy and productive lives