The Physiological and Behavioral Effects of Separation on Horses

1
The Physiological and Behavioral Effects of
Separation on Horses Megan Jenness, Margaret
Maddux, Chaundra Schofield, David Matlack, DVM,
Sarah Muhrer and Nathan Trueblood,
Ph.D. Department of Biology, Earlham College,
Richmond, IN 47374

• METHODS
• Behavioral Assessment
• Behavioral reactions were recorded on videotape
  from inside the pasture.
• Increased stress was measured behaviorally as
  decreased time spent grazing increased time
  spent walking/trotting, and increased time with
  the head up.
• For each session, a random five-minute section of
  videotape was chosen for measuring the amount of
  time spent for each behavioral trait.
• Physiological Assessment
•  
• Baseline physiological assessments were performed
  in the barn before horses were turned out.
  Repeat measures were performed after 15 minutes
  and then again at the end of the interval (45
  minutes).
• Physiological stress was evaluated by measuring
  heart rate, respiratory rate, body temperature,
  and cortisol levels. Increases in these
  parameters may indicate stress.

• SUMMARY
•  
• Heart rate, respiratory rate, and cortisol
  levels were significantly elevated when horses
  were separated from the herd.
• All behavioral measurements were significantly
  different between separation and herd. 

Trot/Canter
other
Walking Head Down
Standing Head Up
Walking Head Up
CONCLUSIONS   Our data are consistent with the
conclusion that domesticated horses become
physiologically stressed when separated from the
herd.

• IMPLICATIONS
• Data from this and further studies may yield
  mechanistic insight into the persistence of
  herding behavior in domesticated animals.
• Increased understanding of the effects of
  turning a horse out to pasture may cause horse
  owners to change the way they handle their
  animals, as increased cortisol levels lead to
  immune suppression and decreased organ function
  other stress associated hormones have been shown
  to cause heart kidney pathologies.
• FUTURE DIRECTIONS
• Extend the observation time Is the stress
  acute/persistent?
• Compare responses of herd familiarized and
  solitary horses

Cortisol (mcg/dl)
Heart Rate Monitoring A heart rate monitor
(Polar S-610) was used to record heart rate data
transmitted from a horse-specific heart rate
transmitter. Respiration Respiration was taken
by counting the rise of the thoracic cavity for a
15 second time period.
Figure 2. Serum cortisol levels were elevated in
horses separated from the herd. pherd baseline.
Respiratory Rate (breaths per minute)
Temperature Temperature was taken rectally with
a digital thermometer.
ACKNOWLEDGMENTS We gratefully acknowledge the
owners of the horses used in this study Bob
Holcomb, Sonja Bigalke, Megan OConnel, Brad
Cully, Melinda Doster, Leslie Cooperman, Emily
Devey. Many thanks go to the EC Bio Department,
Earlham College Stables, Susie Cayard DVM and
Family Pet Health Center, Tom Newton DVM, and EC
safety and security maintenance. Financial
support from the EC HHMI grant and the Stephenson
Student/Faculty Research Fund made this work
possible. Thank You!.
Baseline Separated Herd
Figure 3. Respiration rate was increased in
horses separated from the herd. p herd
BIBLIOGRAPHY  Taimor et al.Hypertrophy-associated
gene induction after beta-adrenergic stimulation
in adult cardiomyocytes. Mol Cell Cardiol. 2001
Mar33(3)503-11. Breist, W., et al.Cardiac
remodeling after long term norepinephrine
treatment in rats.Cardiovasc Res. 2001
Nov52(2)265-73. J. F. Hurnik, A.B. Webster,
and P.B. Siegel. Dictionary of Farm Animal
Behavior. Iowa Iowa State University Press,
1995.   Pavord, Tony and Marcy. The complete
equine veterinary manual. United Kingdom David
and Charles, 1997.   Reef, Virginia D.V.M.
"Large animal cardiology." University of
Pennsylvania School of Veterinary Medicine.
http//cal.nbc.upenn.edu/lgcardiac/. Retrieved
from the World Wide Web November 15,
2001.   Hamilton, W.D. Geometry of the selfish
herd. J. of Theor. Bio. 31, 295-311 (1971).
Blood Sampling Jugular venous catheters were
implanted the evening prior to experiments. Blood
samples were drawn using heparinized vacutainers.
Blood tests were performed by an independent
veterinary testing lab (IVDL).