According to recent studies, horse owners are missing early signs their horses and ponies are becoming overweight until they are dangerously obese. This means they are putting their horses at risk and making weight loss programs more difficult
In this article, Dr Jennifer Stewart, an equine veterinarian and researcher who specialises in equine nutrition, discusses in detail the importance of keeping horses in a healthy condition, how the body condition scoring system is used to assess the state of each animal and the steps you can take to successfully monitor your horse’s body condition to maintain optimal health.
The illustrated version of this article contains tables and other useful information.
The truth about fat
Obesity is becoming a major health concern in horses (and people) all around the world, and is increasingly recognised as a serious equine welfare issue because it compromises their long-term health and performance. In most instances, horses become overweight because they are given the opportunity to consume more calories than they need.
Certain breeds of horses are more prone to weight gain and require even more careful management to try to prevent this energy imbalance from occurring.
Horses (and ponies), like humans and other animals, will eat to meet their energy requirements. But, if the feed is palatable and high in energy-density, some horses – like individuals of all species – will eat more than is needed. Energy in excess of requirements is stored as fat (ah and don’t we know it!). And, fat is not an inert tissue.
Previously thought to be simply a way for the body to store fat, adipose tissue (the medical name for ‘fat’) is, in fact, a dynamic organ that produces hormones and chemicals.
Fat secretes many nasties with such horrifying names as tumour necrosis factor, cytokines and interleukins – all of which increase inflammation in the body. Fat cells also summon white blood cells to the fat tissue, further increasing production of inflammatory chemicals and compounds. Normally, these hormones and chemicals are activated in response to invading bacteria and infections. In obesity, however, they cause disease.
Overweight horses are more prone to colic, laminitis, foaling and hormonal problems, tire more easily, are less agile and have reduced reproductive ability.
Body condition scoring
The Body Conditioning Scoring (BCS) scale was developed in the 1980’s by Don Henneke, PhD, to evaluate the condition of broodmares. The scale goes from 1 to 9 – where 1 is emaciated and 9 is obese.
Although there are variations, depending on age, activity level and type of horse, (which will be discussed later in the article), a BCS of 5 in the Henneke scale is considered ideal for a horse that is receiving moderate exercise.
Mares with a body condition score (BCS) of 7 or above ovulate less frequently, reducing their ability to get in foal. Carrying excess weight also increases joint, tendon and ligament strain, cancer, skin, heart and circulatory difficulties, risk of strangulating lipoma (where accumulations of fat inside the body twist and cause colic) and decreases resistance to diseases – all of which reduce life expectancy and quality.
In people, obesity is related to high blood pressure, increased risk of cancer, circulatory problems, stroke and diabetes, to name just a few.
Although figures are not available for horses, in people, mortality at any age is 9%, 25%, 65%, 230% and 1,200% greater for people who are 15%, 25%, 40%, 55% or 100% overweight.
Whether obesity causes these effects in horses is unknown, but it probably does.
One of the few benefits of excess body fat is the improved ability of fat horses to keep warm in cold climates. Due to the insulating properties of body fat, as well as its availability as an energy source, horses BCS 7-9 require less supplemental feed during cold weather than horses of lower BCS. This, however, also causes increased heat stress in hot weather. Horses of BCS 7.5 have difficulty dissipating heat in a hot and humid environment (31.5oC, humidity 43.8%), compared to horses with BCS 5.2.
There are also negative relationships between body fat, athletic performance and soundness, including:
- Horses of BCS 7.5 have higher heart rates and longer recovery times after exercise, than horses with BCS 5.2.
- Fatter horses also have higher respiration rates following a 30-minute workout of walk, trot and canter in an indoor arena.
In overweight children, a reduction in body weight of just 5% increased exercise ability by almost 35%. A BCS of 4.5-5 is most consistently recommended for horses engaged in moderate to intense exercise.
The laminitis connection
From a veterinary perspective, there are only two types of pony in the world: ponies that have foundered and ponies that are going to founder!
Ponies evolved in the cold areas of northern Europe and England, surviving extremes of cold and a scarcity of feed. They evolved by adjusting their glucose metabolism, and developing a hearty appetite and the ability to shunt blood away from their feet.
One of the hormones released by fat cells is leptin. Its normal role is to shut down appetite. Obese horses and ponies are often resistant to leptin, and continue to be hungry and eat – even though leptin is pumped out at higher and higher levels.
Today, these traits increase risk of laminitis, making it important to prevent excess condition year-round, and identify increases as early as possible so you can change their management accordingly. Prevention is better than cure, and the sooner you can identify any weight increase, the earlier and easier it will be to get your horse or pony’s condition under control.
The link between obesity and laminitis has long been recognised and research found ponies of BCS 7.8-8.4 have a reduced ability to use glucose, which is instead stored as fat – and this progressively worsens. The reduced ability to use glucose, also known as ‘insulin resistance’ or dysregulation, is similar to diabetes in humans.
Laminitis and founder are, in simplified ways, the equine equivalent of diabetes – insulin resistance leading to impaired blood flow, blood clots, glucose starving, and the degeneration and breakdown of the laminae inside the hooves.
Obese horses with high body condition have high blood glucose, overproduction of insulin and abnormal thyroid levels – a hormonal profile similar to that of a type II diabetic human. In horses, body condition scores above 6 in the Henneke scale are a risk factor for metabolic syndrome, insulin resistance and laminitis.
Body condition and weight estimation in horses
Assessing ‘fatness’ is aided by the use of one of four systems:
- The body condition scoring (BCS) system,
- Measuring girth and length,
- Weight tapes, and
- Measuring girth, belly and rump.
To establish a relationship between body condition and body weight, in the 1980’s, Dr Henneke subsequently developed body condition scoring.
The BCS was originally developed to assess the fatness of pregnant Quarter Horse mares. It had been noted that, as horses gain weight, fat is laid down in a predictable pattern and the location of stored fat is a big clue as to how much excess fat the horse has.
First, horses will protect major organs with fat, then fat is laid down behind the shoulder, then over the ribs, on the rump, along the back and, finally, on the head and neck.
The BCS system is based on visual appraisal and palpable fat cover at six areas of the horse’s body.
The Henneke system assigns a number to fat deposits in specific sites on the horse’s body – the neck, withers, shoulder, ribs, loin and tailhead. (See images and table on the previous pages).
The neck allows for refining of the BCS. As horses gain condition, fat is firstly deposited along the top of the neck, followed by all the way round, then the crest and throat latch.
The shoulder also helps refine the BCS, especially if conformation factors have made other areas less helpful. As horses gain weight, fat is deposited around the shoulder, so it blends smoothly with the body. As condition increases, fat is deposited behind the shoulder, especially in the region behind the elbow.
The back and the rump both have a generous layer of fat on top of the muscle. Rump fat changes quicker than rib fat in weight gain and weight loss. Increasing fat depth at the rump or tailhead is correlated with an increasing body condition score – a one unit change in BCS corresponds to a 0.5cm alteration in rump fat thickness.
BCS is also affected by the horse’s diet and season
In Thoroughbred geldings, fewer body areas can be used to accurately predict BCS. You only need to assess the neck, shoulders, ribs and tailhead.
Wither and loin fat are less reliable indicators of percentage body fat, indicating that Thoroughbreds store fat on the neck before the loin, shoulder, ribs, tailhead and withers.
Horses store more fat on the neck and withers when they are on high-fat/high-fibre diets than when they are fed high-starch/high-sugar diets, and the neck score is often higher than the withers and loin through Autumn and Winter.
The loin area of Thoroughbreds and Quarter horses is affected by the level of exercise, which changes the musculature of the back and the appearance of the back as the muscles build. Loin area is also a poor guide in mares fed for weight gain and shows little change, even as they gain condition from BCS of 6 to 9.
In addition to the traditionally-evaluated areas of fat, it also helps to look at bone size. Light-boned horses tend to carry less fat and have longer, leaner muscles. They will look leaner overall than a horse with big bones and bulky muscles, and they will weigh less as well.
Using the Australian body condition scoring system of 1-5, the ideal score for endurance horses is 1.5-2.5, for polo ponies 2-2.5, equestrian horses 3-4, broodmares 2.5-4 and show horses 4.
An Australian study showed a positive relationship between girth and weight, and between length and weight, allowing estimation of body weight from these measures. Charts have been developed that use BCS and wither height. The tables on Page 66 show the body weight estimates for horses of different heights.
Different systems for predicting weight in horses
Weight tapes: These are available in most saddleries and feed shops. Measurements should be taken with the tape snugly around the girth at the end of respiratory expiration. Weight tapes, however, are unreliable for foals, miniatures and high-withered horses.
Measuring girth: When a weight tape is not available, an ordinary tape measure can be used with the table that appears on the next page, from ‘Feeding and Care of the Horse’ by Lon Lewis.
Measuring girth and length: Another method, which is reasonably accurate, uses length (from the point of the shoulder to the point of the buttock) and girth (taken immediately behind the elbow), and converts this with a formula. This is explained in detail on the Horses and People Weight Calculator.
Body composition studies have shown body fat percentages range from 5.1-19.9% in thin condition horses, 7.4-11% in moderately thin horses (BCS 4-4.9), 12-24% in moderate to fleshy horses (BCS 5-6.9) and 16.4-31.3% in fleshy to obese horses (BCS 7-9).
Mature mares, especially broodmares, have higher body fat percentages (12-16%) than other horses and younger mares (8-11%). So, horses with 7-9 BCS can have over 20% more fat, which means more inflammatory chemicals and greater risk of metabolic derangement.
BCS systems, which measure fat, may not be very accurate for assessing weight loss in ponies. They provide no information on muscle mass or tone, cardiovascular fitness or athletic conditioning, and do not tell you how fit your horse is for competitive performance.
A system to assess muscle development has been developed by Progressive Nutrition. Called Topline Evaluation System (TES), it rates the muscle mass over the back, loin, croup, hindquarters and stifles. For more information, go to: https://bit.ly/2WU4afC
Gaining weight just requires an increase in calories, whereas losing weight requires a reduction in calories – a simple enough principle.
Restricting feed intake, however, results in loss of fat and muscle. So, whether we want to gain muscle or lose fat, the glycaemic index and the amino acid composition of the diet are important.
By reducing calorie (carbohydrate) intake, such as grains, pollard, rice-bran, etc., and fine-tuning protein intake, such as soybean meal, cottonseed meal, lucerne etc., we can reduce fat without losing muscle mass.
Reduction in the BCS of overweight horses is essential to their long-term health, performance and wellbeing.
Weight loss through feed restriction and/or exercise improves insulin sensitivity – reducing the chance of reproductive problems and laminitis, and improving exercise tolerance.
The key to managing equine obesity is to monitor body weight and/or BCS. While successful weight loss can be difficult to achieve and/or maintain with some horses and ponies, the simplest method is to reduce calorie intake.
Feeding 65-70% of the energy required for their ideal body weight will facilitate weight loss and should result in a reduction in BCS of one score per month.
Low- to medium-quality grass hay, plus a mixture of vitamins and minerals to balance the low copper, zinc, salt, selenium, vitamin E and vitamin A concentrations commonly found in mature forages, is a good and sound approach to healthy weight loss.
Horses on pasture can be fitted with grazing muzzles or just turned out from early to mid-morning when pasture sugar levels are lowest. Voluntary exercise can be encouraged by increasing paddock size and providing paddock mates.
Riding 3-4 times a week for 30 minutes is also beneficial, but take care when exercising overweight horses because they can have trouble breathing and overheat easily – keep it slow and gentle, with rests if respiration becomes rapid. Also keep an eye on their joints, tendons and ligaments.
Diets for weight loss should never include starvation – not even for six hours. Always provide roughage. Ponies are at risk for a usually fatal condition called hyperlipaemia, which is triggered by the withholding of feed. Always maintain roughage intake above 1% of bodyweight and spread the intake over as long a time as possible using slow feeding systems.
In overweight ponies, grassy meadow hays are an answer. They are high in fibre, they take a long time to chew, so the pony happily thinks it has eaten a lot and its gut does too, but calorie and protein intake have not been excessive. Hay made from sugar-rich grass can have high levels of sugar. These can be removed by soaking the biscuit for 16 hours. But don’t discard the water into dams or creeks because it has an oxygen demand many times that of sewerage and it will pollute the water.
Because horses have a great psychological need to chew, dieting can lead to an increase in weaving, wood-chewing, crib biting and bedding eating. Letting them have social contact, providing ‘toys’ and regular exercise will reduce the risk.
The article by Prof Simon Bailey, a leading researcher in the link between insulin and laminitis, also gives information and management tips and the good news is that reducing condition can prevent future laminitis episodes in at-risk horses and ponies.
Allowing body condition to fall below a score of 1.5 is likely to compromise a horse’s welfare. During Winter, a long, heavy hair coat can obscure body condition and you may need to run your hands over the horse to get an accurate body condition score.
Expert tip for checking the weight loss program is working:
According to Dr Pat Harris, equine nutrition specialist and lead researcher for the Waltham Centre for Pet Nutrition in the United Kingdom, a good way to monitor the progress of the weight-loss program for the more obese horses and ponies is to measure their heart girth (near the wither), belly girth (half way on the barrel) and rump width (over the top of the rump from point of hip to point of hip) regularly and keep a record.
Initially, this may work better than BCS, because in the early stages of the weight-loss programme, the horse’s BCS may not actually reduce despite them starting to lose weight.
This, most likely, is because at the early stages, they lose the ‘invisible’ internal fat first, rather than the external fat that you can feel and score during a BCS assessment.
In addition, periodic body weight measurement preferably using a calibrated weighbridge (e.g. at a local vet practice) can be very helpful.
- When measuring, consistency is more important than detail.
- Ensure the horse is fully comfortable with the process
- Have the horse relaxed, standing in the same position in the same environment (ideally a flat surface)
- Measure at the same time of day in relation to feeding and exercise.
- Measure at the same site on the animal (as far as possible and in the same orientation, e.g. for weigh tapes you tend to measure at a slight angle but heart girth measurement tends to be more vertical).
- Take several measurements and consistently at the end of and expiration, and calculate the average.
What about adding condition?
Poor body condition is not always due to lack of feed, but could be related to parasites, dental problems, chronic injury or illness or lack of mobility, due to arthritis or lameness affecting the horse’s ability to graze.
For healthy horses with low bodyweight, however, the most common cause is not feeding enough calories daily.
The first step should always be to estimate the horse’s weight, score his or her body condition, and do a calorie count. If the horse is emaciated, a veterinary examination and dental check-up are recommended.
When you calculate the amount of feed your horse requires each day, a good rule of thumb is to feed 1.5-2.5% of their body weight of feed and roughage.
For a 500kg horse, that is between 7.5 and 15kg daily. To increase weight, it may be necessary to feed up to 3% in bodyweight of roughage.
To avoid digestive disturbances and laminitis, weight gain should be managed gradually and with correct dietary management. An increase in condition on a healthy, but thin, horse can be easily achieved by feeding a balanced diet with adequate amounts of a nutrient-dense, highly digestible feed.
So, now you know how to use the body condition scoring system! It is helpful to do it with friends, so you can discuss the scoring. The closer you agree, the more accurate and confident you will become.
Preventing horses from getting too forward in condition is always easier, cheaper, less time-consuming and less painful than trying to induce weight loss.
Becoming familiar and well-rehearsed with using the body condition scoring system provides valuable information on how your horse is doing, and whether you need to fine-tune and adjust energy intake to promote optimum health and performance for life.