Grazing Muzzles: An Effective Solution for Horses with Insulin Dysregulation?

A new study from the University of Kentucky provides valuable insights into the use of grazing muzzles for horses suffering from insulin dysregulation (ID). Already widely used to limit grass intake and help prevent metabolic disorders, grazing muzzles now appear to play an important role in reducing insulin spikes while horses are turned out on pasture.

Why Use a Grazing Muzzle?

Insulin dysregulation is now recognized as one of the primary risk factors for endocrinopathic laminitis in horses. Owners of insulin-dysregulated, overweight, or laminitis-prone horses are constantly looking for ways to reduce the intake of sugars found in pasture grass.

According to a nationwide survey conducted in the United States involving 559 horse owners and managers across 44 states, more than 91% of respondents had used some form of restrictive grazing strategy. The two most common methods were:

• Grazing muzzles (81.5%)
• Dry lots (81.3%)

The most frequently cited reasons for using grazing muzzles were preventing laminitis and controlling body weight.

Interestingly, respondents felt that grazing muzzles offered better welfare outcomes than other restrictive management practices, such as stabling, dry lots, or arena turnout. Most horses wore their muzzles for 9 to 12 hours per day, primarily during the spring and summer months.

A Study to Measure the Impact on Insulin

To go beyond owner observations, doctoral researcher Morgan Askins and colleagues investigated the actual effect of grazing muzzles on insulin responses in horses diagnosed with insulin dysregulation.

The study was conducted in late summer 2025 and included nine horses of mixed breeds and sexes, with an average age of 19 years. All horses had confirmed insulin dysregulation based on an oral sugar test. Two of the horses were also diagnosed with PPID (Pituitary Pars Intermedia Dysfunction, commonly known as Equine Cushing’s Disease).

Researchers compared two situations:

• Horses grazing without a muzzle
• Horses grazing while wearing a muzzle

Each horse served as both a control and treatment subject, improving the reliability of the results.

During sampling days, the horses were monitored over a 10-hour period, from 9:00 a.m. to 7:00 p.m. Blood samples were collected every two hours to evaluate:

• Plasma insulin levels
• Blood glucose levels
• Environmental and pasture-related factors

The pasture contained non-structural carbohydrates (NSC) ranging from 6% to 13.8%, with an average grass height considered optimal for grazing.

Highly Encouraging Results

The findings revealed a clear difference between the two groups.

Horses Without Grazing Muzzles

Insulin concentrations steadily increased throughout the day, from 11:00 a.m. until 7:00 p.m. This pattern is commonly observed in horses that are sensitive to the sugars present in pasture grass.

Horses Wearing Grazing Muzzles

In contrast, insulin levels decreased between 9:00 a.m. and 11:00 a.m. and remained consistently low for the rest of the study period.

In other words, restricting grass intake through the use of a grazing muzzle significantly reduced insulin responses in horses with insulin dysregulation.

What Does This Mean for Horse Owners?

These results further support the use of grazing muzzles as an effective management tool for metabolically challenged horses.

When used correctly, grazing muzzles can:

✅ Allow continued access to pasture and natural movement

✅ Reduce consumption of sugar-rich grass

✅ Limit insulin spikes associated with laminitis risk

✅ Support weight management in overweight horses

Of course, a grazing muzzle should not be viewed as a standalone solution. It works best as part of a comprehensive management strategy that includes:

• Regular veterinary monitoring
• Appropriate pasture management
• A balanced nutritional program
• An exercise plan whenever possible

More Research Is Needed

The researchers emphasize that additional studies are necessary to better understand the effectiveness of grazing muzzles under different conditions, including:

• Pastures with higher sugar concentrations
• Different seasons of the year
• Comparisons between warm-season and cool-season grasses
• Separate analyses of horses with insulin dysregulation alone versus those with both ID and PPID

Despite these limitations, the study provides strong evidence that grazing muzzles can be a valuable tool for reducing insulin responses in horses with insulin dysregulation.

Conclusion

Long considered simply a weight-management tool, grazing muzzles are now demonstrating significant metabolic benefits. For horses prone to insulin dysregulation and endocrinopathic laminitis, they offer a practical way to maintain pasture access while reducing the physiological impact of excessive sugar intake.

This is encouraging news for horse owners seeking to balance equine welfare, turnout time, and metabolic health.

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Sources

1. Nancy S. Loving, DVM. Research Evaluates the Prevalence and Efficacy of Grazing Muzzles for ID Horses, EquiManagement, August 14, 2026. Available at: https://equimanagement.com/research-medical/metabolic/research-evaluates-the-prevalence-and-efficacy-of-grazing-muzzles-for-id-horses/

2. Askins, Morgan J. Managing Dietary Nonstructural Carbohydrates in Insulin Dysregulated Horses: Pasture, Long-Stem Forage, and Restrictive Grazing Strategies (2026). University of Kentucky, Gluck Equine Research Center. Available at: https://uknowledge.uky.edu/gluck_etds/74

3. Askins, M.J., Harris, P.A., McClendon, M.E., Adams, A.A. Short-Term Effects of Grazing Muzzles on Insulin in Horses with Insulin Dysregulation out at Pasture. Journal of Equine Veterinary Science, 2026, Article 106095. DOI: https://doi.org/10.1016/j.jevs.2026.106095.