Author ORCID Identifier

http://orcid.org/0000-0002-6867-6483

Year of Publication

2021

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Agriculture, Food and Environment

Department/School/Program

Veterinary Science

First Advisor

Dr. Amanda Adams

Abstract

Insulin dysregulation (ID) is the main risk factor for the development of hyperinsulinemia-associated laminitis (HAL). ID in the equid has been extensively researched; however, recommendations for diagnosing and managing ID horses have originated from work completed in other models, such as the ID pony and healthy horse. Therefore, our overall objective was to improve current diagnostic tools and nutritional management strategies by investigating the effect of season, the fed and fasted state on the oral sugar test (OST) and dietary nutrient content on insulinemic responses in the ID horse. To address this, four main objectives with three specific aims were examined. (OB1) To determine if season effects insulin concentrations in the ID horse. ID horses’ morphometric measurements did not change across season; however, seasonal changes in basal (T0) and post-OST (T60) insulin concentrations were detected. ID horses had higher T0 and T60 insulin concentrations in the spring compared to the fall and summer and winter had higher T60 insulin compared to the fall. Seasonal changes should be considered when diagnosing and monitoring ID status. (OB2) To determine if a higher (HD) dose of oral sugar would improve the diagnostic ability of the OST. (OB3) In addition to a higher dose, the fed (FE) and fasted (FA) state prior to the OST was examined to determine if fasting has an impact on basal and post-OST insulin concentrations. ID horses had higher insulin concentrations compared to NID for all OST performed. There were no differences between the low dose and HD OST for ID horses. ID basal insulin for FE was higher vs. FA OST, but FE or FA post-OST insulin was not different in ID horses. Finally, (OB4) investigated ID horses’ insulinemic responses to varying nutrient concentrations, in order to improve current nutritional recommendations for ID horses. ID horses had greater insulin responses compared to NID horses for all dietary treatments. NSC appears to be the main driver in the postprandial insulinemic response in the ID horse. ID horses appear to have threshold for pure sources of NSC greater than 0.1 g/kg BW. This body of work added to the current understanding of how-to diagnosis, monitor, and nutritionally manage ID horses.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2021.445

Funding Information

Maxwell Henry Gluck Equine Research Center (no: 809000015981) from 2017-2018.

MARS horsecare (no: 3048113252) from 2017-2021.

Lincoln Memorial University Veterinary College (no:1013209520) in the summer of 2021.

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