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Author ORCID Identifier
https://orcid.org/0009-0003-1972-7234
Date Available
5-20-2026
Year of Publication
2026
Document Type
Doctoral Dissertation
Degree Name
Doctor of Philosophy (PhD)
College
Agriculture, Food and Environment
Department/School/Program
Veterinary Science
Faculty
Amanda A. Adams
Faculty
Emma Adam
Abstract
Insulin dysregulation (ID) is a complex endocrine disorder, impacting a large percentage of the equine population. ID is the defining characteristic of equine metabolic syndrome (EMS). Within the various classifications of EMS horses, the commonality is ID and their higher risk of laminitis. To mitigate insulin response and laminitis risk in ID horses, current management focuses on restricting pasture exposure and feeding low nonstructural carbohydrate (NSC) rations. Minimal studies have evaluated how ID horses respond to pasture of various NSC, long-stem forages, and restrictive grazing strategies. Providing horse owners and managers with improved nutritional management recommendations for ID horses with scientific validation is essential in managing this devastating condition proactively.
The objectives were to 1) measure insulin concentrations in response to seasonal changes in pasture NSC in ID and non- ID (NID) horses over 24-hour grazing periods, and in ID horses being moved from the spring pasture to a dry lot, 2) investigate the effects of meal feeding long-stem forage with various NSC content on the insulin response in ID and NID horses, 3) determine how commonly and why different types of restrictive grazing methods are used in the US, and 4) evaluate how utilizing grazing muzzles in ID horses influences their insulin response to fresh forage over a 10h summer grazing period.
Insulin concentrations were monitored in n=6 ID and n=6 NID horses across two 24h grazing periods in late summer and spring. Elevated pasture NSC was associated with increased insulin concentrations in ID horses. Although different from ID horses, some NID horses had notable elevated insulin responses. Glucose significantly differed by time and horse metabolic status during grazing periods. Moving ID horses from pasture to housing on a dry lot with a low NSC hay, resulted in rapid and sustained reductions in insulin concentrations within 24h.
The effect of meal feeding six, long-stem forages with various NSC content on the insulin response in n=5 ID and n=5 NID horses was evaluated in a 5-week randomized crossover study. Peak and delta insulin for ID horses were significantly greater for all dietary treatments compared to NID. Despite two long-stem forages having NSCs of ≤9% on an as fed basis, there was an increased insulin response compared to the negative control. Results suggest feeding a forage >0.13 g NSC/kg BW/meal may produce an increased insulin response in ID horses.
A nationwide survey of 559 respondents found that restrictive grazing methods are widely utilized in the US. Most survey participants were female, ages 30-39, who currently owned, leased or cared for 2-5 equids. 91% of respondents had utilized a restrictive grazing method, most commonly grazing muzzles and dry lots to prevent/manage laminitis or prevent equids from becoming overweight. Grazing muzzles were most frequently used 9-12h in the spring and summer, compared to 0h in the fall and winter.
The effect of grazing muzzles on insulin responses was evaluated in n=9 ID horses during four, 10h summer grazing periods. In a replicated 2x2 crossover design, ID horses had significantly lower insulin concentrations when grazing with a muzzle compared to unmuzzled controls, despite moderate pasture NSC levels. Insulin responses were influenced by treatment, time, and their interaction, with substantial individual variability observed.
Collectively, the results from this work highlight seasonality, forage NSC content, forage intake, and grazing management strategies influence insulin responses in ID and NID horses differently. These studies show the use of dry lots with low NSC hay, and the use of grazing muzzles can be effective tools for reducing the insulinemic response in ID horses. However, the need for ongoing monitoring of health and insulin responses of ID horses remains essential due to fluctuations in NSC and individual metabolic differences, as changes can occur rapidly.
Digital Object Identifier (DOI)
https://doi.org/10.13023/etd.2026.272
Archival?
Archival
Funding Information
These studies were supported by Mars Petcare and the University of Kentucky, Department of Veterinary Science.
Recommended Citation
Askins, Morgan J., "MANAGING DIETARY NONSTRUCTURAL CARBOHYDRATES IN INSULIN DYSREGULATED HORSES: PASTURE, LONG-STEM FORAGE, AND RESTRICTIVE GRAZING STRATEGIES" (2026). Theses and Dissertations--Veterinary Science. 74.
https://uknowledge.uky.edu/gluck_etds/74
