Weight Management in Horses
Any discussion of weight in horses requires an understanding of Body Condition Scoring (BCS) as a means of communicating.
The diagram below illustrates the areas we use to categorize the body condition of an individual horse. Each condition is then described:
Description of Body Condition Scores
Poor: Animal extremely emaciated; backbone, ribs, tailhead, hip joints and pelvis projecting prominently; bone structure of withes, shoulders, and neck easily noticeable; no fatty tissue can be felt.
Very Thin: Animal emaciated; slight fat covering over base of spine but spine, ribs, tailhead, hip joints and pelvis prominent; withers, shoulders and neck structure obvious.
Thin: Fat present about halfway up on the backbone, very slight fat between the ribs but ribs easily discernible. Tailhead is prominent but individual vertebrae cannot be identified visually; hip joint rounded but discernible, lower pelvic bones more rounded. Withers, shoulders and neck accentuated.
Moderately Thin: Slight ridge along back. Faint outline of ribs discernible and tailhead prominent but with some fat.
Moderate: Back is flat. Ribs not visually distinguishable but easily felt. Fat around tailhead beginning to feel spongy. Withers appear rounded; neck and shoulders blend smoothly into body.
Moderately Fleshy: May have slight crease down back. Fat over ribs spongy: fat around tailhead soft; fat beginning to be deposited along the side of withers, behind shoulders and along sides of neck.
Fleshy: May have crease down back; individual ribs can be felt, but noticeable filling between ribs with fat; fat around tailhead soft; fat deposited along withers, behind shoulders and along neck.
Fat: Crease down the back; difficult to feel ribs; fat around tailhead very soft; area along withers filled with fat; area behind shoulder filled with fat; noticeable thickening of neck; fat deposited along inner thighs.
Extremely Fat: Obvious crease down back. Patchy fat appearing over ribs; bulging fat around tailhead, along withers, behind shoulders, and along neck. Fat along inner thighs may rub together; flank filled with fat.
Use of the Weight Tape
Stand the horse on a flat surface with legs squared and balanced under the horse.
Handler should maintain the horse with the head and neck in a normal position.
Tape is placed over the withers, then straight down vertically to just behind the elbow, around the girth area and directly back up to the top. The position should be identical with each measurement.
Managing the Underweight Horse
A Body Condition Score (BCS) below 4 represents the beginnings of a compromised immune status of the horse along with lowered reproductive efficiency and
In horses with weight loss due to dental problems we often find gingivitis and periodontal disease. These oral infections are exacerbated by the decreased
immune status of an underweight horse. Other infections also tend to become more serious.
Thin broodmares cannot keep up with the nutritional needs of a growing foal during pregnancy or the increased caloric demands of lactation,
and they are less likely to conceive following re-breeding.
Diagnosis and Management
Lab work, a full physical exam, a fecal examination for parasites, and a complete dental exam are indicated.
Separation of the underweight horse from more dominant, healthy individuals is warranted, but close proximity may be necessary to avoid anxiety on the part of the underweight horse.
Sudden feed changes may cause colic. A gradual increase in quality and quantity of food should be developed with the cooperation of caretaker and veterinarian. Special senior concentrates may be indicated for the older horse or horses with missing or diseased teeth.
A balanced vitamin/mineral supplement should be given (Ranch0Min, GrowStrong, Purina 12-12+) daily.
Use the weight tape every two weeks, and keep a chart.
Managing the Overweight Horse
A horse with a BCS of 8 or 9 will have decreased athletic performance. These horses heat up sooner and sweat more. They also have decreased reproductive
efficiency. Additionally, obesity exacerbates any existing musculo-skeletal problems.
Weight reduction Guidelines:
First, have your annual hay supply analyzed for protein, fat, fiber, and carbohydrate levels. We recommend
Equi-analytical Labs in New York.
Their website with sample sheet is available Here. We recommend the #601—Equi-tech analysis
which costs $26.00. Feel free to have a copy emailed to us so we can help you with the results and formulate a ration if needed.
Caretaker must have a weight tape, a scale to weigh food and a weight chart.
All feed is measured by weight every feeding.
Each body condition score is about 40# in a 1000# horse—You should plan on your horse losing at least 2 BCS scores, or approx 80-100 pounds.
Work toward feeding the minimal requirement of 1% of body weight. A 1000# horse should get 10# total of grass hay daily, after a 1 week period of adjustment. (No grain or concentrates past minimal amount needed to supply minerals and vitamins). Any concentrate used should be low carbohydrate: Ranchway’s Sound Starch, any Senior ration, Nutrena’s Safe Choice, Triple Crown’s Low Starch. You shouldn’t use more than 1 cup twice daily.
Maintain or increase regular exercise regimen. Discuss any lameness issues with your veterinarian.
Weigh the horse every two weeks using weight tape and keep chart. Adjust hay amount based on loss of weight. About 3-5 months of dietary and exercise correction usually needed to safely correct obesity.
Care must be taken with Minis, ponies and donkeys. Fat metabolism may be affected by diet and liver problems can develop.
Equine Metabolic Syndrome and the overweight horse
This condition has previously been called Peripheral Cushing’s Syndrome. Horses that fit this picture have sometimes been incorrectly thought of as
It is usually seen in obese horses of middle age, but it can be diagnosed in horses as young as 6-8years. Body type typically seen is individuals with a
cresty neck, and fat at the shoulders, over the rump and in geldings in the sheath. These horses also have excessive intra-abdominal fat (omentum) that
can be detected by ultrasound exam. Mares and geldings are equally affected. Mares with EMS are notoriously hard to breed and have irregular cycles.
Breed predilections to Equine Metabolic Syndrome include ponies, Spanish Mustangs (Barbs), Pasos, Warmbloods, Saddlebreds and Morgans.
Horse with EMS have a PREDISPOSED TO LAMINITIS (founder). Often this is the reason the veterinarian is called. Metabolic Syndrome must be suspected
with onset of laminitis when there is no other obvious inciting cause.
How does it happen?
Fat cells (adipocytes) in the omentum secrete a hormone called HSD. This hormone increases the amount of circulating cortisol in the body.
Increased cortisol causes insulin resistance meaning that the insulin is no longer as effective in metabolizing glucose which causes hyperglycemia.
Additionally, the increased insulin levels may have a direct effect in the foot. The hyperglycemia causes changes in the endothelium
(lining of blood vessels), increased endothelin-1 and decreased Nitrous Oxide. This changes the elasticity of vessels and increases formation of
blood clots. Blood supply to the laminae, the connection of the hoof wall to the bones of the feet, is compromised and cell death begins.
There is progressive weakening of the attachment of the hoof wall to the coffin bone with inflammation, pain and ultimately possible rotation of
the bone downward.
TESTING FOR EMS: Blood insulin and glucose samples after 12 hour fast:
Fasting insulin usually over 250 (Normal insulin levels are 29-179 pmol/L )
Usually slight to moderate glucose elevation
Weight reduction. See Management of the Overweight Horse, above
Increased exercise as permitted by state of lameness. Exercise improves insulin effectiveness.
Anti-oxidants Vit E 10K IU per day; Vit C 5K IU per day
Temporary thyroid supplementation to increase rate of metabolism and weight loss and to reduce the effects of high insulin in the blood.
Other additives sometimes suggested are not proven to be effective in horses. i.e., chromium, vanadium, magnesium