Behavior Genetics of the Horse (Equus caballus) - Genetics and the Behavior of Domestic Animals - page 278

allowing the foal to learn this way, the first author observes reduced or almost
non-existent lateralized responses to handling both at this early stage of train-
ing, and in subsequent training conducted as the horse matures.

CONCLUSION
The field of behavioral genetics has the potential to uncover both genetic
and environmental influences on normal and abnormal behavior ( Hausberger
et al., 2011 ; Zentner and Shiner, 2012 ). Behavioral

genetic methods are
based on a foundation of methods that are beginning to explain mechanisms
of complex traits. As specific genes are identified, researchers can begin to
explore how these interact with environmental factors in development. Only
a few decades ago, equine scientists believed that most characteristics of
horse behavior were almost entirely the result of environmental influences.
Many of these characteristics are now known to be genetically influenced,
in many cases to a substantial degree. Learning ability and memory, novelty
seeking, activity level, fearfulness and sociability all show some degree
of genetic influence. Behavioral geneticists are interested in understanding
differences among individuals. Some genetic factors may cause small differ-
ences, and others may cause large differences. Such differences may be
caused by environmental factors and/or by one or many genes. Studying
behavior in this way is especially important when selecting horses for breed-
ing. Understanding how and why behaviors are developed and learned can
play a large part in the breeding program. Inheritance of temperament is
high, but in comparison to other domestic animals, selection for temperament
in horses is less common. Breeding stallions with good performance traits
but bad temperament traits is not always a good idea. A difficult tempera-
ment can hinder performance. Balanced selection for performance traits,
conformation traits, and temperament traits is important. A large body of
evidence shows that selection for any single trait has unwanted effects on
other traits (see Chapter 1).
Environmental factors can affect fetal brain development; therefore,
reducing stress in pregnant mares is important. Evidence showing psycholog-
ical stress (fear stress) in mothers during gestation has effects on fetal brain
development occurring mainly through changes in hormone profiles. Stress
hormones enter the fetal bloodstream and change brain structure and function
leading to increased sensitivity to stress. When fetal brain circuits are highly
plastic, external influences are more pervasive.
Forced contact following birth affects emotional development, causing
insecure attachment to the mare, and disrupts normal social behavioral devel-
opment with peers. Forced contact can also shape how foals perceive
humans. Perception of humans as “potentially threatening” may last a
lifetime in reactive and fearful foals. Research shows that foals respond
differently to intensive handling. Genetic differences in temperament may