Biology Reference
In-Depth Information
Chapter 7
Behavior Genetics of the Horse
(
Equus caballus
)
Mark J. Deesing
*
and Temple Grandin
†
*Grandin Livestock Handling Systems, Inc., Fort Collins, Colorado, USA;
†
Department of
Animal Science, Colorado State University, Fort Collins, Colorado, USA
INTRODUCTION
Why do horses behave differently from each other? People have debated this
question for centuries. Some believe that horses behave as they do according
to inborn tendencies; others think it's because they're taught. A recently fast-
growing body of evidence makes it clear that both sides are partly right.
Nature (genetics) endows horses with inborn abilities and traits, and nurture
(experience and upbringing) takes these genetic tendencies and molds them
as a horse learns and matures. Now the debate is centered on how much of
horse behavior is shaped by genes and how much by the environment.
Although genes play a role in shaping behavior, they never determine
it. This is because genes only directly code for proteins, not behavior.
However, a change in a single protein code can cause a host of downstream
effects and may even bring about a distinct phenotype (
Keane et al., 2011
).
Horses are not very convenient laboratory animals. However, many
genetic principles discovered by researchers studying mice or humans in the
laboratory are also relevant in horses. In order for behavioral scientists to
tease apart the genetic and environmental influences on complex traits such
as temperament, it is important to use large numbers of horses controlled for
genetics (age, sex, sire) and environment (stable or pasture housing, type of
feed, type of work, caretakers, etc.). Three recent studies brilliantly meet
these requirements and show the advancements made in the study of behav-
ior genetics.
MOLECULAR BEHAVIOR GENETICS
Momozawa et al. (2005)
conducted a molecular genetics study on tempera-
ment in 136 two-year-old thoroughbred horses (73 males and 63 females)
kept at a single training farm in Japan. The horses were at the same stage of
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