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Home / Equine Research Bank / Animals (Basel) / Eye Blink Rates and Eyelid Twitches as a Non-Invasive Measur...
Animals : an open access journal from MDPI2019; 9(8); 562; doi: 10.3390/ani9080562

Eye Blink Rates and Eyelid Twitches as a Non-Invasive Measure of Stress in the Domestic Horse.

Abstract: Physiological changes provide indices of stress responses, however, behavioural measures may be easier to determine. Spontaneous eye blink rate has potential as a non-invasive indicator of stress. Eyelid movements, along with heart rate (HR) and behaviour, from 33 horses were evaluated over four treatments: (1) control-horse in its normal paddock environment; (2) feed restriction-feed was withheld at regular feeding time; (3) separation-horse was removed from visual contact with their paddock mates; and (4) startle test-a ball was suddenly thrown on the ground in front of the horse. HR data was collected every five s throughout each three min test. Eyelid movements and behaviours were retrospectively determined from video recordings. A generalized linear mixed model (GLIMMIX) procedure with Sidak's multiple comparisons of least squares means demonstrated that both full blinks (16 ± 12 vs. 15 ± 15 vs. 13 ± 11 vs. 26 ± 20 full blinks/3 min ± SEM; a,b differ < 0.006) and half blinks (34 ± 15 vs. 27 ± 14 vs. 25 ± 13 vs. 42 ± 22 half blinks/3 min ± SEM; a,b,c differ < 0.0001) decreased during feed restriction, separation and the startle test compared to the control, respectively. Eyelid twitches occurred more frequently in feed restriction ( < 0.0001) along with an increased HR ( < 0.0001). This study demonstrates that spontaneous blink rate decreases while eyelid twitches increase when the horse experiences a stressful situation.
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Publication Date: 2019-08-15 PubMed ID: 31443315PubMed Central: PMC6721043DOI: 10.3390/ani9080562Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research article studies the potential of utilizing eye blink rates and eyelid twitches as a non-invasive method for identifying stress levels in domestic horses.

Research Objectives

  • The study aimed to identify stress in horses using their spontaneous eye blink rate and eyelid twitches. This is proposed as a simpler alternative to other physiological changes that are traditionally used as an index of stress.
  • The researchers put forward the hypothesis that the frequency of full and half blinks might reduce and eyelid twitches might increase in conditions that cause stress in the horse.

Methodology

  • The study was carried out on 33 horses across four different scenarios designed to test stress levels. The scenarios were the control condition (normal paddock environment), feed restriction, separation (from paddock mates), and a startle test (a ball thrown suddenly).
  • Each test lasted three minutes. During this time, the horses’ heart rate data was collected every five seconds.
  • Eyelid movements and behaviors were recorded on video for retrospective determination of changes.
  • Statistical analysis was carried out using a generalized linear mixed model with Sidak’s multiple comparisons of least squares means.

Findings

  • The study found that both full and half blinks decreased during the feed restriction, separation, and the startle test as compared to the control scenario.
  • It was noted that eyelid twitches increased significantly when the horse underwent feed restriction, accompanied by an increase in heart rate.
  • This suggests that a decrease in spontaneous blink rate and an increase in eyelid twitching may be directly tied to stressful situations.

Implications

  • This research provides a new non-invasive behavioral method to measure stress in horses, which can be particularly helpful for equine care and management.
  • The findings indicate that monitoring these particular eyelid behaviours could serve as an effective marker for identifying acute distress and potentially for predicting future stress responses.

Cite This Article

APA
Merkies K, Ready C, Farkas L, Hodder A. (2019). Eye Blink Rates and Eyelid Twitches as a Non-Invasive Measure of Stress in the Domestic Horse. Animals (Basel), 9(8), 562. https://doi.org/10.3390/ani9080562

Publication

Animals : an open access journal from MDPI
ISSN: 2076-2615
NlmUniqueID: 101635614
Country: Switzerland
Language: English
Volume: 9
Issue: 8
PII: 562

Researcher Affiliations

Merkies, Katrina
  • Department of Animal Biosciences, University of Guelph, Guelph, ON N1G 2W1, Canada. kmerkies@uoguelph.ca.
  • Campbell Centre for the Study of Animal Welfare, University of Guelph, Guelph, ON N1G 2W1, Canada. kmerkies@uoguelph.ca.
Ready, Chloe
  • Department of Animal Biosciences, University of Guelph, Guelph, ON N1G 2W1, Canada.
Farkas, Leanne
  • Department of Animal Biosciences, University of Guelph, Guelph, ON N1G 2W1, Canada.
Hodder, Abigail
  • Department of Animal Biosciences, University of Guelph, Guelph, ON N1G 2W1, Canada.

Conflict of Interest Statement

The authors declare no conflict of interest.

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