Stereotypic Behaviors and Physiological Indicators of Stress Occur in Horses with Restricted Durations of Turnout

Authors

Elizabeth E. Rodgers, University of Nebraska-LincolnFollow

First Advisor

Lena Luck

Committee Members

Dustin Yates, Ruth Woiwode

Date of this Version

5-2025

Document Type

Thesis

Citation

A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Animal Science

Under the supervision of Professor Lena Luck

Lincoln, Nebraska, May 2025

Comments

Copyright 2025, Elizabeth E. Rodgers. Used by permission

Abstract

The confinement of horses to stalls with limited or no turnout time restricts their natural roaming behaviors, which potentially increases stress and behavioral stereotypies. This study investigated the impact of turnout duration on behavioral and physiological stress indicators in healthy horses. Adult horses (n = 11) were enrolled in a 3 treatment (0-, 15-, and 60-minute turnout/day) Latin square design, including 3 12 d experimental periods over 6 weeks. Horses were acclimated to turnout (24.38 x 64.01m indoor arena) and stalls (2.74 x 4.87m - 3.66 x 3.66m) stalls prior to data collection on day 1. Experienced handlers managed the turnout of horses and had no issues with catching or releasing them. Behavioral data were collected by video and assessed through ethograms. Physiological measures included heart rate variability (HRV) and differential complete blood counts. Statistical analyses were conducted by ANOVA using repeated measures and multiple comparisons t-tests with Fisher’s LSD. Analyzing turnout treatments (15 and 60 minute turnout/day), heart rate variability measurements were decreased (p < 0.05), including RR-interval, RMSSD, pNN50 in the 15-minute treatment compared to 60-minute treatment, indicating a state of stress. Assessing stalled data (0, 15, and 60 minute turnout), LF/HF power (a measure of HRV) was lowest (p < 0.01) with 60-minute turnout compared to 0- and 15- minute turnout, indicating a relaxed state. Blood cell analyses uncovered an increase in MCHC (p = 0.04) during 15-minute turnout, indicating an acute stress response. This result is consistent with a trend (p = 0.06) in circulating leukocytes, increasing during 15-minute turnout compared to 0- and 60-minute turnout. Behavioral assessments in stalls showed that when horses received 60-minute turnout, they tended to exhibit less (p = 0.1) stalled locomotion than when receiving 15-minute turnout. Stereotypic and aggressive behaviors were variable but did not differ among turnout times. A limitation of this study was an inability to analyze the complete behavioral data set (video footage). These findings demonstrate that restricted turnout durations influence physiological and behavioral stress indicators in horses. Specifically, 15 minutes of daily turnout appeared to be associated with unique stress responses. The longer turnout duration of 60 minutes appeared to mitigate this physiological stress, which highlights the importance of adequate daily turnout time in horse management practices.

Advisor: Lena Luck