An overabundance of fat along the top of the neckline, otherwise known as cresty neck, is an indicator of metabolic problems in your horse.
In fact, researchers believe this type of regional fat deposit (nuchal crest adiposity) is a strong indicator of equine metabolic syndrome (EMS).
Recognizing cresty neck in your horse early on is important as EMS can put your horse at risk for developing the potentially debilitating disease, laminitis.
If your horse has already developed a cresty neck, the good news is that there are measures you can take to reduce this fat accumulation. Feeding, exercise, and management practices can all help to get rid of a cresty neck because they improve insulin sensitivity.
By doing so, you will also reduce your horse’s chance of developing other complications related to metabolic disease. For help with addressing your horse’s cresty neck, submit their information and feeding program for analysis online.
What Causes Cresty Neck in Horses?
Horses that have cresty neck are usually described as easy keepers or over-conditioned.
In addition to being overweight, horses with a cresty neck may have some form of metabolic dysfunction or insulin resistance.
When there is too much sugar or starch in the diet (hydrolyzable carbohydrates), they are converted to fat which is stored in fat deposits including the top of the neck. Even some of the volatile fatty acids produced during forage fermentation can be converted to fat. Over time, this area becomes enlarged and hardens.
Simple sugars and starch are hydrolyzable carbohydrates (HC). This means they can be digested and absorbed in the small intestine, contributing to insulin peaks. Insulin promotes fat storage in specialized cells called adipocytes.
Sugar and starch are found in lush grasses, hay, grains, concentrates, and treats. High HC feeds can contribute to and exacerbate cresty neck size.
Researchers are not exactly sure why horses develop this adiposity along the top of the neck. However, they believe that it may be a repository for long-term fat storage.
Horses with cresty neck may also develop fat pockets over the tail head, above the eyes, behind the shoulders, and/or around the sheath in the case of male horses. This fat tissue not only stores energy but also synthesizes and secretes hormones that affect metabolism and insulin function. 
Horses with cresty neck may or may not have generalized obesity. One study found that obesity status (body condition score) and cresty neck condition were highly associated. In that study, 97.5% of obese horses and 59.6% of non-obese horses had cresty neck. 
There appears to be a genetic link to EMS and cresty neck, with certain breeds such as Welsh, Dartmoor, and Shetland ponies, as well as Andalusians, Morgans, Mustangs, Arabians, Haflingers, Icelandics and gaited breeds being more susceptible to insulin resistance.
These breeds tend to utilize glucose very efficiently, which ensures they have plenty of energy reserves when food is scarce. This also puts them at risk of greater fat accumulation if their diet supplies excess digestible energy. 
With that said, overfeeding, insufficient exercise, and mineral imbalances can all play a part in the development of cresty neck and it can occur in any breed.
Equine Metabolic Syndrome (EMS)
Regional adiposity, such as a cresty neck, is thought to be the strongest external identifier of EMS. 
EMS is also linked with obesity and insulin resistance (IR). It prediposes horses to laminitis that is not caused by grain overload, colic, or overloading of a limb caused by injuries such as fractures. EMS horses may also have elevated triglyceride levels.
When horses are insulin resistant, this means that the cells in their muscles, fat, and liver do not respond well to insulin and take less glucose from the blood for energy. To make up for it, the pancreas then makes more insulin. Over time, blood sugar levels increase.
When EMS horses consume a high-HC diet, their bodies produce higher than normal levels of insulin and are slow to return to baseline values. These clinical signs were previously called hypothyroidism, peripheral Cushing’s disease, prelaminitic syndrome, or Syndrome X.
As mentioned previously, EMS horses are more susceptible to laminitis, which can be quite serious in some cases. In fact, up to 25% of equine euthanasia is associated with laminitis. 
EMS can be diagnosed by a veterinarian in one of several ways:
- Blood glucose tests;
- Blood insulin level;
- Oral sugar test (OST);
- Insulin tolerance test (ITT); and/or
- Radiographs to confirm presence of laminitis or changes in the feet.
For older horses especially, it’s important to rule out PPID (formerly known as Cushing’s disease) by measuring ACTH concentration or their response to thyroid releasing hormone which causes an exaggerated ACTH level in PPID horses. However, horses can be affected by both EMS and PPID at the same time.
Scoring a Cresty Neck
Body condition scoring (BCS) has long been the most common method for assessing total body fat on a horse. Henneke’s nine-point scale is the most widely used scoring system for assessing BCS.
The Henneke body condition scoring system also lists a cresty neck as a sign of obesity. We have no way of knowing how many of the horses they looked at had EMS but cresty neck without obesity or a high cresty neck score indicate EMS.
Recently, researchers developed a way to measure neck crest fat with a 5-point scoring system known as the Cresty Neck Score (CNS). Horses are considered healthy with a score of 0-2, while a score of 3 or greater indicates metabolic dysfunction.
Cresty Neck Scoring System
Cresty necks are scored as follows: 
0 — No palpable crest.
1 — No visual appearance of crest but slight filling felt with palpation.
2 — Noticeable appearance of crest but fat deposited fairly evenly from poll to withers. Crest easily cupped in one hand and can be bent from side to side.
3 — Crest enlarged and thickened so fat is deposited more heavily in middle of neck than toward the poll, giving a mounded appearance. Crest fills cupped hand and begins losing side to side flexibility.
4 — Crest grossly enlarged and thickened and can no longer be cupped in one hand or easily bend from side to side. Crest may have wrinkles or creases perpendicular to the topline.
5 — Crest is so large that it droops to one side (called a fallen crest).
Implications of CNS
The Cresty Neck Score (CNS) is simple, but it does require an experienced person to give consistent scores.
One study showed that ponies with a CNS of 3 or greater were five times more likely to be insulin resistant than those with a CNS below 3. These scores were not related to the horses’ BCS. 
An interesting phenomenon with CNS scores is that they may change throughout the year. Another study found that CNS scores were higher at the end of winter months as compared to the end of the summer.
This is the opposite of general obesity; BCS scores tend to be highest after summer and lowest after winter mont