Link Between Nutritional Deficiencies And Behavior In Horses

Understanding how nutrition influences horse behavior is something I’ve spent a lot of time thinking about as a horse owner and enthusiast. A horse’s diet is closely linked not only to physical health but also to attitude, anxiety levels, and trainability. This connection is well documented in scientific literature. Ignoring nutritional basics can lead to behavioral issues that complicate handling and management.

Nutrition’s Role in Horse Behavior

The relationship between nutrition and behavior is well-supported by scientific studies. For example, McKenzie et al. (2017) highlight that diet composition directly influences equine temperament and reactivity. I’ve observed subtle changes in my horses’ behavior within days of altering their feed or supplement routine. When diets lack essential nutrients, horses may become irritable, anxious, or display abnormal behaviors.

A horse with a balanced diet displays habits like regular eating, keen interest in the environment, consistent energy, and a relaxed attitude in the stable. When certain vitamins or minerals fall short, these patterns can switch up. Horses might become skittish, show signs of aggression, chew on wood, or develop unusual repetitive habits known as stereotypies.

Nutrition is one of the few behavioral determinants we can control. Thoughtful feed management is key to fostering calm, trainable horses.

Common Nutritional Deficiencies Affecting Horse Behavior

Some deficiencies are especially linked to mood problems or behavior changes. Here are a few important ones:

• Magnesium: Deficiencies are linked to heightened stress responses, nervousness, and muscle tremors. Horses under stress or consuming lush pasture (low in magnesium) are particularly at risk (Harris et al., 2017).
• Thiamine (Vitamin B1): Essential for nervous system function. Horses on high-grain, low-forage diets may show irritability or reduced focus due to insufficient thiamine (Pagan & Jackson, 1996).
• Vitamin E: Vital for nerve and muscle health. Low levels may result in reduced willingness to work or subtle neuromuscular issues (Divers et al., 2008).
• Selenium: Important for muscle function. Deficiencies can lead to lethargy or resistance, but oversupplementation is toxic (Geor et al., 2013).
• Iron and Copper Imbalance: Poor coat quality and withdrawn behavior may stem from imbalance between these minerals (Geor et al., 2013).
• Fiber Deficiency: Inadequate forage intake can increase risk of stereotypies, as seen in studies by Nicol et al. (2002).

How Deficiencies Lead to Specific Behavior Changes

Behavioral signs that hint at a nutritional deficiency in horses aren’t always obvious at first. From my experience, tracking changes in routine, attitude, or performance can reveal hidden dietary blind spots.

• Anxiety and Nervousness: Horses lacking magnesium or B vitamins often seem jumpier, harder to settle, and less able to recover from small surprises. Multiple studies ( Harris et al., 2017 and Pagan & Jackson, 1996) point out that magnesium and thiamine are central to nervous system regulation, directly affecting reactivity and tone.
• Lethargy and Lack of Motivation: In cases where vitamin E or selenium runs low, I’ve noticed that horses may resist being tacked up or show less spark on the lunge line. A 2008 study in Journal of Veterinary Internal Medicine details slower responses and a “flat” affect, making both exercise and training sessions less enjoyable for both horse and handler. (Divers et al., 2008)
• Aggression and Irritability: Sometimes, simple shortages like not enough forage, or imbalances in dietary energy, cause unexpected pushiness or unwillingness to cooperate. Foraging habits and gut health are both linked to behavior. (McGreevy et al., 2009)
• Development of Stereotypies: Horses lacking adequate fiber or certain trace nutrients may develop vices like cribbing, weaving, or wood chewing. (Nicol et al., 2002).

When these patterns crop up in my own barn, I start by reviewing what’s being fed and adjusting based on forage analysis and professional guidance. Noticing a sudden switch in attitude might be your first clue to dig into potential nutritional gaps and make small but meaningful changes.

Practical Steps for Prevention and Correction

Making sure a horse doesn’t fall short on key nutrients starts with good management and attention to detail. Here’s what I do when assessing a feeding program for possible gaps:

1. Forage First: High-quality hay or pasture provides fiber and base nutrients. Testing forage is key.
2. Balanced Concentrates: Grain and pelleted feeds should be fortified with vitamins and minerals.
3. Monitor and Adjust: Track behavior alongside diet. Sudden changes can hint at dietary imbalances.
4. Targeted Supplementation: Use lab tests to identify specific deficiencies before supplementing. Oversupplementation can harm.

Common Situations Where Deficiencies Happen

Nutritional gaps tend to turn up during specific times or in certain management setups:

• Early Spring and Summer: Fast growing pasture can lack some minerals, especially magnesium. Horses with restricted turnout or on sandy soil are more likely to show symptoms.
• Heavy Workloads: Performance, show, or racehorses sometimes burn through B vitamins and electrolytes, requiring extra support.
• Senior Horses: May absorb nutrients less efficiently (Brosnahan & Paradis, 2011). They need regular reviews of diet and perhaps age appropriate supplements
• Horses on High Grain Diets: Diets with too much starch or too little roughage upset gut microbes and can lead to shifting B vitamin availability, increasing irritability and gastric ulcers (Valberg et al., 1999).

Case Study: Behavioral Improvement with Magnesium Supplementation

Horse: 10-year-old gelding, used for trail riding and light dressage.

Issue: Spooky, nervous behavior under saddle, muscle twitching noted after work.

Intervention: Bloodwork showed borderline magnesium levels. Added magnesium supplement (3000 mg/day) and reduced starchy grain.

Outcome: Notable improvement in relaxation, reduced startle response, improved softness in the bridle within two weeks.

Tips to Identify and Address Behavioral Shifts

Starting with a behavior log can really help. Each time I notice a change, I take notes on diet changes, environment, and even workload. I then check out these possible solutions:

• Ask a vet or equine nutritionist to review the feed program and suggest testing for possible deficiencies.
• Use forage or hay analysis to check for missing nutrients, especially when changing hay lots or moving yards.
• If several horses in a barn show similar changes, consider whether a new shipment of feed or supplements is the cause.

I’ve found that small tweaks, like changing hay sources or adding a trace mineral block, often make a noticeable difference in horses’ attitudes and performance. Checking in with professionals and making gradual changes is key.

Frequently Asked Questions

Question: How soon can I expect to see behavioral changes after fixing a deficiency?
Answer: Some changes appear in days (e.g., reduced spookiness); others, like improved coat condition, take weeks.

Question: Is supplementing always the answer?
Answer: Not always. Overdoing supplements causes its own problems. The first step is to have your forage and current ration analyzed, then supplement only what is truly lacking, as advised by a nutritionist or veterinarian.

Question: Can behavioral problems be due only to diet?
Answer: Not always. Training, environment, and routine changes all play a part. Nutrition is a controllable factor worth evaluating.

References:

• Brosnahan, M. M., & Paradis, M. R. (2011). Assessment and management of the geriatric equine patient. In D. M. Traub-Dargatz & N. M. Giguère (Eds.), Equine Geriatric Medicine and Surgery (2nd ed.). Saunders.
• Divers, T. J., Barton, M. H., Gardner, R. B., et al. (2008). Equine motor neuron disease: Pathophysiology, clinical features, and diagnostic evaluation. Journal of Veterinary Internal Medicine, 22(3), 476–481. https://doi.org/10.1111/j.1939-1676.2008.0089.x
• Geor, R. J., Harris, P. A., & Coenen, M. (2013). Equine Applied and Clinical Nutrition: Health, Welfare and Performance. Saunders Elsevier.
• Harris, P. A., Bailey, S. R., Elliot, J., Longland, A., & Thompson, K. (2017). Practical feeding management of horses with an emphasis on controlling glycaemic and insulinaemic responses. Equine Veterinary Education, 29(8), 491–504. https://doi.org/10.1111/eve.12674
• McGreevy, P. D., et al. (2009). The role of learning theory in equitation. Equine Veterinary Journal, 41(4), 350–356.
• McKenzie, E. C., Firshman, A. M., & Valberg, S. J. (2017). The role of diet in the prevention and management of equine myopathies. Applied Animal Behaviour Science, 190, 57–64.
• Nicol, C. J., Badnell-Waters, A. J., Bice, R., et al. (2002). The effects of diet and weaning method on the behaviour of young horses. Applied Animal Behaviour Science, 78(4), 293–306. https://doi.org/10.1016/S0168-1591(02)00102-1
• Pagan, J. D., & Jackson, S. G. (1996). The role of vitamins in equine nutrition. Proceedings of the Kentucky Equine Research Nutrition Conference, 3, 53–70.
• Valberg, S. J., Naylor, J. M., & Roberts, M. C. (1999). Feeding management and nutritional considerations in horses with chronic muscle disorders. Journal of Animal Science, 77(Suppl 2), 52–59. https://doi.org/10.2527/1999.77suppl_252x