Date on Honors Thesis

Fall 11-14-2025

Major

Animal Science

Examining Committee Member

Shea Porr, PhD, Advisor

Examining Committee Member

Lydia O'Sullivan, PhD, Committee Member

Examining Committee Member

Johanna Choate, DVM, Committee Member

Abstract/Description

Insulin dysregulation is a key component of Equine Metabolic Syndrome (EMS), and is often a predisposing factor to conditions such as laminitis and hepatic lipidosis. Diagnosis of EMS is most often reached through a combination of glucose and insulin measurements in equine serum. Achieving an accurate result of insulin concentration is vital for diagnosis, making proper sample handling essential. The aim of this project was to evaluate the effect of repetitive freeze-thaw cycles on equine serum insulin concentrations. Serum was collected from 10 university-owned horses and split into four treatment groups: Unfrozen, Once Frozen, Twice Frozen, and Thrice Frozen. Unfrozen serum was sent immediately for analysis and the other samples were maintained in a regular freezer (0 ℉, -18 ℃) for the freeze-thaw process. Once the freeze-thaw cycles were complete, all frozen samples were sent to the laboratory for radioimmunoassay analysis. Data were analyzed using the MIXED procedure of SAS. The concentration data were analyzed for main effects of sex, age, and freeze-thaw cycle. There was an effect of age on serum insulin concentration (P < 0.0001). Older horses had higher concentrations than younger (28.7458 ± 1.7998 uIU/mL and 51.6967 ± 2.3236 uIU/mL, respectively), which was in agreement with other published results. There was no effect of freeze-thaw cycles, which was similar to previously reported studies in other species. There was also no effect of sex, which was not in agreement with previous reports where mares were reported to have higher serum insulin concentrations than geldings. The results of this study will equip veterinarians and laboratories to freeze equine insulin serum samples up to three times and still have confidence in the accuracy of their results.

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