What is Chromium?
Chromium is a trace mineral that assists in the body’s utilization of carbohydrates and fats, which are important sources of energy (calories). Recently, the primary interest in chromium as it relates to horses is in its role as a potentiator of insulin to facilitate glucose clearance. More simply put, chromium makes insulin more effective at moving glucose from the blood into tissues, like muscle or fat storage.
The Role of Insulin in the Horse
Insulin helps maintain a horse’s blood glucose levels within in a tight range. When blood glucose is elevated, like after your horse eats, the pancreas secretes insulin to move glucose into muscle or fat storage. This is a normal and needed function; however, sometimes this process doesn’t work correctly and insulin builds up in the blood. High levels of insulin in the blood is a problem because it significantly increases the likelihood that a horse will experience laminitis. Laminitis is inflammation inside the hoof, which is a very painful and potentially life-threatening condition.
Chromium in the Horse’s Diet
Chromium is a nutrient that has been identified by the Nutrient Requirement of Horses (NRC, 2007) as being dietarily essential; however, the authors determined that there was not enough data at the time of publication to determine a minimum daily requirement and that no evidence of a chromium deficiency had been identified in horses. This suggests that there is enough chromium in the horse’s base diet, coming naturally from the ingredients, to support their basic needs. However, there is the possibility that additional chromium added to the diet could be beneficial to your horse. Providing a minimum amount of a given nutrient to prevent deficiency does not always equal an optimal diet to support your horse’s performance and wellness.
Sources of Supplemental Chromium
To take a look into the chromium research that has been published in horses, we first need to understand the differences in sources of supplemental chromium. There are many sources of chromium, but only two that are found in horse products in the United States today.
- Chromium propionate – the only source of chromium approved for use in horse feeds by The Association of American Feed Control Officials (AAFCO) and the FDA. It is approved for use at 4 mg per day.
- Chromium yeast – found in some horse supplements, but does not have approval for use in complete feeds.
Research Findings on Chromium Propionate
Research for chromium propionate in horses is limited. The study that was used to get FDA approval for the use of chromium propionate in horses (Spears et al., 2020) supplemented chromium at 4 different levels (0, 2, 4 and 8 mg per day) to healthy horses. They found that insulin sensitivity improved, compared to the control treatment, (0 mg) at 2 and 4 mg of chromium per day, but not at 8 mg of chromium per day. Serum chemistry measures did not indicate that horses were harmed by feeding up to 8 mg of supplemental chromium propionate per day; however, it is not clear why insulin sensitivity is poorer at 8 mg of supplemental chromium propionate per day as compared to 2 and 4 mg of supplemental chromium propionate per day. Feeding levels higher than 8 mg of supplemental chromium propionate per day has not been studied and would not be advisable based on the current research findings.
Does Chromium Propionate Control Insulin Levels in Horses with Equine Metabolic Syndrome?
The short answer - we don’t know. With the understandings that we have about how chromium works in the horse’s body, it is logical to think that it could help horses with Equine Metabolic Syndrome or Insulin Resistance. However, to date, data has not been published that shows the impact of chromium propionate on horses with Equine Metabolic Syndrome. The safety data referenced above only used healthy horses.
There are multiple underlying mechanisms that cause high blood insulin in hoses. Poor peripheral insulin sensitivity is one, where the body’s transporters that move glucose from the blood into tissue storage don’t respond to normal levels of insulin, which leads the body to continue producing more insulin. While certain levels of chromium propionate (2 and 4 mg/day) assists in this process in healthy horses, we don’t know if we would observe similar behavior to chromium supplementation with insulin insensitive horses.
Other causes of high blood insulin would be less likely to be responsive to chromium supplementation. In some cases, horses display poor liver clearance of insulin, meaning the body produces normal levels of insulin and transporters respond correctly to those levels, but once that insulin is no longer needed, the body does a poor job of removing it from the blood stream. In other cases, excess insulin is produced due to malfunctions in the action of hormones like incretin, which are produced in the gut, that cause the pancreas to overproduce insulin.
It has been proposed that chromium supplementation in healthy horses may prevent the development of insulin resistance later in life, but there is no data to support this claim.
Research Findings on Chromium Yeast
While chromium yeast is not approved for use in complete feeds, it is found in horse supplements. There is significantly less regulatory oversight for horse supplements as compared to horse feeds.
In one study, insulin resistance in ponies was slightly improved with chromium yeast, but even with improvement, the ponies were still insulin resistant (Vervuert et al., 2010). In another study, a supplement containing chromium yeast and magnesium propionate did not improve insulin resistance in ponies with a history of laminitis (Chameroy et al., 2011).
Chromium yeast has been found to inconsistently impact exercise recovery in healthy horses (Pagan et al., 1995; Vervuert et al., 2006).
Can Chromium Negatively Impact Horses?
In most horses, the ability to clear blood glucose more quickly would generally be considered a positive thing; however, there is a group of horses with a genetic disorder that makes them abnormally sensitive to insulin. This genetic disorder is Polysaccharide Storage Myopathy Type 1 (PSSM Type 1). It is caused by a mutation in an enzyme that is responsible for storing glucose in their muscles as glycogen. The mutation causes the enzyme to be overactive, resulting in the constant production of glycogen. In these horses, glycogen is stored in an abnormal form, so the horse is not able to break it down for energy during work, which leads to the symptoms of the disease – muscle soreness and tying up. Chromium’s role in facilitating greater glucose entry to cells would be counter productive to controlling PSSM Type 1 symptoms and, instead, may worsen symptoms. In these horses, we aim to minimize glycogen storage by feeding low sugar & starch (NSC) diets and providing daily exercise.
The Bottom Line
Chromium supplementation may be beneficial for some, but not all horses. There is still much that needs to be researched about the impact of chromium in horses.
If you have a horse that may be a candidate for chromium supplementation, be mindful of the concentration of chromium propionate in the product you are using and the rate that you are feeding that product in order to gain maximum benefit (4 mg maximum per day). Chromium propionate inclusion in variable feeding rate products can lead to under or over supplementation. The impact of over supplementation of chromium propionate is not fully understood.
If you have questions about your horse’s diet, please reach out to us for a personalized feeding plan!
Chameroy, K. A., Frank, N., Elliott, S. B., & Boston, R. C. (2011). Effects of a supplement containing chromium and magnesium on morphometric measurements, resting glucose, insulin concentrations and insulin sensitivity in laminitic obese horses. Equine Veterinary Journal, 43(4), 494-499.
NUTRIENT REQUIREMENTS COUNCIL. (2007). Nutrient requirements of horses.
Pagan, J. D., STEPHEN G. Jackson, and STEPHEN E. Duren. "The effect of chromium supplementation on metabolic response to exercise in thoroughbred horses." In Proc. 14th Equine Nutrition and Physiology Symposium, pp. 96-101. 1995.
Spears, J. W., K. E. Lloyd, S. E. Pratt-Phillips, P. Siciliano, and K. Krafka. "43 Safety of chromium propionate as a source of supplemental chromium for horses." Journal of Equine Veterinary Science 100 (2021): 103506.
Vervuert, I., D. Cuddeford, and M. Coenen. "Effects of chromium supplementation on selected metabolic responses in resting and exercising horses." Equine and Comparative Exercise Physiology 3, no. 1 (2006): 19-27.
Vervuert, I., Osswald, B., Cuddeford, D., & Coenen, M. (2010). Effects of chromium yeast supplementation on postprandial glycaemic and insulinaemic responses in insulin-resistant ponies and horses. Pferdeheilkunde, 26(2), 245-250.