Overweight horses are a common issue in New Zealand. Carrying too much condition has many negative health aspects: the most frequent being laminitis, but also respiratory stress, over loading joints, movement difficulty, loss of stamina and the potential onset of metabolic problems.
Excess blood glucose and insulin are the factors in overweight animals and can develop into insulin resistance, endocrine complications such as Cushing’s disease or EMS (Equine Metabolic Syndrome) (Frank ,2009). Equine metabolic syndrome (EMS) is important because of its association with laminitis. Obesity and insulin resistance are two important components of EMS. So, increasing insulin sensitivity will lower high blood insulin levels and restore optimal metabolic health and reduce the risk of laminitis and EMS (Grenager, 2021).
When a horse becomes overweight the effect of insulin is lowered and so it reduces the ability of a horse’s metabolism to convert fat to muscle.
Some horses are more disposed to becoming overweight by nature, the easy-going laid-back horse that doesn’t get excited and doesn’t have high energy levels, usually called good doers, is one that is vulnerable to being overweight.
Genetics can play a part as some breeds and particularly ponies are likely to be overweight, often progressing to EMS. Miniature ponies are known to be very vulnerable to laminitis, EMS and/or Cushing’s disease. (Durham, et al., 2019). In particular they are vulnerable to a progressive lipid state that can be fatal.
In essence, too much feed, especially non-structural carbohydrates i.e. sugars, combined with a low exercise regime will result in a fat horse or pony. The result is quite visible.
Ultrasound can be effectively used to measure stages of overweight (Westervelt, 1976). Aso a mathematical formula can be used (Carroll & Huntingdon, 1988) :
Estimated Weight (kg) =
The original guide was produced by Henneke in 1983 and is a 9 point scale:
 |  |
Ref: Henneke condition chart.
It is not an option to literally starve a horse or pony by penning or stabling without feed for large parts of the day. Horses need to have some form of feed passing though their stomach or ulcers will be a result (Husted et al., 2008). It is important to act quickly when first signs of weight gain appear.
Hay is a useful alternative to too much pasture, but it must be washed to remove sugars and a mineral supplement along with Vitamin E, given as washing removes them. Using a grazing muzzle, turning out on long pasture, (as short or mown has concentrated sugars.) An exercise regime is needed. If a horse or pony can’t be ridden then large free areas to run around, lunging, access to a walking machine or a swimming pool.
Supplementing with chromium has been shown to be very effective and a result can be seen as the fat pads on the neck and rump are greatly reduced. It improves metabolic conversion resulting less fat stored and converted to muscle (Spears et al. 2020).
For more information read the article ‘The Challenges for the Overweight Horse’
| Active Ingredient | Concentration (%) |
|---|---|
| Trivalent Chromium | 0.03% |
| L-Leucine | 0.40% |
| L-Valine | 0.40% |
| L-Isoleucine | 0.20% |
| Pyridoxine (Vitamin B6) | 0.10% |
| Size | Body Weight (Approx.) | Daily Dose (gm) |
|---|---|---|
| Overweight Horse | 500 kg | 20g |
| Overweight Pony | 300 kg | 10g |
| Overweight Miniature Pony | 150 kg | 5g |
*Enclosed scoop measurement = 15gm
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