Author ORCID Identifier

https://orcid.org/0009-0002-3062-2647

Date Available

7-25-2024

Year of Publication

2024

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy (PhD)

College

Agriculture, Food and Environment

Department/School/Program

Veterinary Science

Advisor

Dr. Amanda Adams

Abstract

Horses are regularly transported across the United States; however, the reasons for travel, trip lengths, and management practices are not well characterized. While long distance transportation has been associated with increased incidences of health-related problems, the impact of short distance transportation on horse health is less understood. Notably, aged horses ( > 15 years) have an altered immune response following short-distance transportation, but this has yet to be compared to young horses. It is also unknown whether transportation stress would alter endocrine responses of horses with metabolic disorders, such as insulin dysregulation (ID) or pituitary pars intermedia dysfunction (PPID).

The objectives were 1) to characterize the how and why horses are transported by road in the U.S., 2) to evaluate differences in stress and immune responses to short distance transportation between aged and young horses, 3) to determine if ID horses have altered endocrine responses following transportation and 4) to characterize the stress response to short distance transportation of horses with and without PPID.

An online nationwide survey was conducted to determine the common types of journeys horses are transported by road in the U.S and how horses are managed on trips 3 hours or less. There were 1294 survey participants with the majority being female, adult, amateurs who owned and transported their own horse for trail/leisure riding. The most common lengths of trip horses were transported was less than one hour, and the frequency of trips was greater for shorter lengths of journeys. While adult horses were transported most often, > 30% of horses were over the age of 15 years. Although owners expressed concerns for horse health during transport, very few monitored vital signs before or after transportation, especially on short journeys.

Differences in short-term transportation stress responses of aged and young horses were explored with 5 aged (22 ± 1 year) and 6 young (2 ± 1 year) horses transported by road on a round trip of 1 hour and 20 minutes. Cortisol and heart rate both increased in response to transportation, with no differences due to age. Additionally aged horses had increased plasma insulin concentrations and altered gene expression of certain cytokines post-transportation compared with young horses.

The stress and insulin response of ID and non-ID horses following transportation were determined by transporting 7 ID and 7 non-ID horses using the same methodology as the previous study. ID horses had increased serum insulin concentrations compared with non-ID horses; however, even non-ID horses had post-transportation and oral sugar test (OST) insulin concentrations above the diagnostic cutoff for ID that could cause misleading diagnostic results.

Finally, certain stress hormones of the hypothalamic pituitary axis of PPID horses were explored to determine the impact of short-distance transportation and diagnostic testing. ACTH remained elevated in PPID horses following transportation; however, transportation increased cortisol in moderately PPID and non-PPID horses but remained low in severely PPID horses.

Overall, the results from this dissertation highlight the importance of understanding the endocrine, metabolic, and physiological responses of horses to the stress of being transported short durations. These studies showed differences in various physiological and endocrine responses to transportation based on age and endocrine disorder and provide justification for why it is necessary to consider these factors when managing and monitoring horses being transported by road or if performing diagnostic testing post-transportation.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2024.371

Funding Information

Graduate Research Assistantship supported by MARS EquestrianTM

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