As a natural prey animal, horses are skittish or can appear anxious for brief periods of time. However, being constantly anxious or nervous is often considered an abnormal behavior.

This can manifest as a horse that is routinely wide eyed, constantly bolts from you, weaves or paces, has body shakes, or develops other vices like wood chewing.

There are multiple factors that can contribute to a horse being anxious. Changes in their feeding or training schedule, introduction of new pasture mates, seasonality in stallions and mares, limited exercise or turnout time, and many others can all cause horses to become anxious. However, diet can be a cause or can exacerbate a horse’s anxiety. With an anxious horse, it is worth the effort to evaluate your feed plan and either adjust it or eliminate it as a contributing factor to this behavior.  

Similar to horses that suddenly become lazy, for a horse that is normally calm and suddenly becomes anxious or nervous, most of the time this can be indicative of an underlying health condition. It is important to always remember with these types of horses you should speak with your veterinarian. If your horse’s behavior rapidly changes, this could indicate a serious illness or injury that is inducing nervousness in your horse. Potential causes could be:

  • Injury
  • Illness
  • Vision problems
  • Low-grade colic
  • Gastric ulcers

An overabundance of calories (energy) in the diet that a horse does not have the opportunity to burn off with activity or exercise can lead to overexcitability and anxiousness. Thus, when evaluating the diet, it is important to understand where the energy in a horse’s diet is coming from. The vast majority will come from the horse’s forage portion of the diet. However, concentrates and even some supplements can also add excess calories. The main contributing nutrient classes for energy are:

  • Fiber (structural carbohydrates). Major source of energy in the diet that is digested in the hind gut with the aid of bacteria. Usually not correlated with excitability in horses.
  • Sugar/Starch (non-structural carbohydrates). Usually higher in concentrates or seeded hays and is a quick burning energy source. Typically correlated with excitability in horses.
  • Fats. Present in forages and concentrates and seen as a longer burning energy source and not a major contributor to excitability in horses.
  • Protein. Once was blamed for causing excitability in horses but now understood to not be a major contributor.

Forage should always be the foundation of any horse’s diet. However, while forage can be a major source of calories in the diet, it is not seen as a “hot” feedstuff, or one that would induce a major and sudden spike in blood sugar (glucose), which could cause excitability in the horse. Yet, if you are concerned, there are strategies to reduce forage intake, such as feeding more often with smaller meals, use of hay nets, or use of a grazing muzzle.

The usual culprit of diet causing excitability in a horse is the concentrate (grain) portion of the diet. Concentrates such as sweet feeds, corn-based diets, those with added molasses or many others that are high in sugars and starches can be considered “hot” feeds. These are ones that when fed in sufficient quantity, cause a surge in blood glucose and cause excitability and anxiousness. With a surge of glucose comes a spike of the hormone insulin, whose role is to cause the horse to use or store glucose. Studies in other species have begun to show that spikes in insulin result in changes of blood chemistry, which cause hyperexcitability.

Though it can be difficult to provide diet recommendations for anxious horses because the cause can be multi-factorial, we still urge you to contact us to speak with our experts for advice. Some broad recommendations would be to feed a quality concentrate with low to moderate non-structural carbohydrates that is higher in fat to ensure your horse receives adequate calories (if necessary).

Finally, it is being marketed to horse owners to feed extra vitamins or minerals to help “calm” your horse. Minerals such as magnesium or extra B-vitamins like thiamine are marketed as helpful in reducing anxiety in your horse. If you are feeding a balanced diet to your horse with a quality concentrate and forage, horses will not need extra vitamins or minerals as their needs are already being met. It will be a rare occurrence with a poor-quality forage and poor concentrate that a horse would need more or such. In fact, feeding too much can be harmful to your animal!

All in all, managing a horse that is constantly anxious can be frustrating for a horse owner. However, evaluating the horse’s diet can be a great way to either find where the diet is contributing to that behavior or will at least help you in eliminating it if it is a contributing factor. Again, if you have any concerns or need help in evaluating your horse’s diet, please contact us for a personalized feeding plan tailored to your horse’s specific needs!

Chris J. Mortensen, Ph.D.