The horse body mass is highly variable, depending on breed, model, physiological state, condition, owner's purpose and usage of the animal. Always 65% to 75% water, it is divided on average between 50% muscle, 11% bone and 10% fat. Depending on whether it's a pony or a draft horse, it can range from less than 200 kg to over a ton, with an average of 500 kg for saddle horses. It also differs with the season, as horses are almost always fatter in summer than in winter. Various tools are used to estimate their weight and body condition, and veterinary scales have been created to determine whether a horse has an ideal body mass according to precise criteria. Thinness is associated with mistreatment, but owner-independent factors such as age and illness can cause dramatic weight loss in horses. In Western countries, equine obesity is one of the major veterinary health problems of the 21st century. It is directly linked to numerous pathologies, such as laminitis, osteoarthritis, insulin resistance and colic. It also favors the development of equine Cushing's disease, and causes a drop in stallion fertility.
General information
The horse body mass is always 65-75 % water. The horse is considered a "thin animal" (with little fat), whose weight is divided into approximately 11% bone, 50% muscle and 9% fat; but a large number of factors influence its weight. Some breeds (draft horses) are naturally heavier than others (ponies), and differ in size and bone structure, so the weight range of horses is highly variable. Ponies can weigh less than 200 kg and heavy horses more than a ton, while the average weight of a saddle horse is estimated at around 500 kg. Champion show-jumper Jappeloup de Luze, for example, weighed around 470 kg. Heavy horses bred for slaughter reach particularly high weights, as it's in the breeder's interest to get maximum meat weight out of them. Weight is also affected by physiological conditions: the horse may be growing, pregnant or breeding. The purpose of breeding and the animal usage also call for different body conditions: for example, a horse destined for sport should always be as close as possible to its ideal weight, to remain a top performer. On the other hand, a pregnant or nursing mare will be in better shape if she has a higher than average body mass, with some fat reserves. Estimating a horse's weight is important in a number of ways for the owner of a domestic horse: dosing its feed ration, administering anthelmintics or other medication, or monitoring its growth and state of health. In these cases, we're talking about the horse's weight, not its health.
Growth Foal growth leads to particularly rapid weight gain in the first few months. At birth, foals weigh 8 to 12% of their mother's live weight. They double their birth weight during their first month of life. By the time they reach weaning age, at around 6 or 7 months, their weight has quintupled. By the age of one, they have reached around 65% of their adult weight and 90% of their adult height, which explains the often gangly appearance of foals at this age. Draft foals fattened for slaughter weigh on average 59.3% of the adult horse's live weight at 8 months, then 70.1% at 12 months, and 90.1% at 30 months.
Seasonal variations
Horses are almost always fatter in summer than in winter, especially if they live outdoors all year round, or in the wild. In summer, changes in light levels lead to an increase in appetite and changes in metabolism, which generally result in weight gain. In winter, on the other hand, appetite is reduced and the efficiency of energy conservation is increased, as the food available is generally scarcer. This particularity seems to stem from the horse's long evolutionary history in an environment that does not always offer the same quantity of food from one season to the next, nor from one year to the next. The obesity rate can differ by around 8% depending on whether measurements are taken in summer or winter. The horse body condition is at its lowest at the end of winter.
Estimating weight and body condition Weight and body condition are two notions that are assessed independently. Along with body dimensions, weight is a component of size.
Estimating weight Weight can be estimated visually, by weighing or by tape weighing.
Visual estimation Visual estimation is the simplest, but it is empirical and often wrong, depending on the experience of the assessor. Consequently, this is the method used by professionals in everyday conditions, without excluding the use of weighing in special situations, notably to monitor animal growth.
Weighing Weighing is the process of estimating weight using specialized weighing equipment. A priori, this is the most accurate method of determining an animal weight, but in the case of a horse, it is necessary to use equipment such as a weighing cage (preferably removable) or a weighing platform. These tools are relatively expensive, and the vast majority of horse owners don't own them. On the other hand, breeders and professionals in the horse market often acquire them, not only for the precision of the measurement, but also to perfect their judgment, through visual appreciation. In breeding areas, some communes are equipped with a weighbridge, which can accommodate a van or cattle truck. Weighing results must also be interpreted according to the assumed state of replenishment of the digestive tract.
Tape weighing Tape weighing is the method of estimating an animal weight using mathematical formulas based on body dimensions. These formulas were devised to compensate for the disadvantages of visual estimation and the constraints of mechanical weighing. They were initially used for educational purposes, in training centers, and as a complement to previous methods. These formulas have generally been developed for adult, mesomorphic animals in a normal state of maintenance and with an average level of digestive tract replenishment. The values collected must therefore be interpreted according to age, body proportions (brachymorphic, mesomorphic or dolichomorphic), state of maintenance and estimated replenishment of the digestive tract. As a result, various scales and mathematical formulas have been created to estimate a horse weight using simple tools, or without tools at all. The tape weighing, placed around the body between the withers and the girth area (corresponding to the thoracic perimeter, TP on the diagram), gives an estimate of weight.
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