Behavioral Genetics in Pigs and Relations to Welfare - Genetics and the Behavior of Domestic Animals - page 420

philosophical rather than a biological concept. During domestication, animals
adapt to agricultural environments via interaction with caretakers and this
genetic change will influence their behavior.
The normal or natural behavior concept is further complicated by the fact
that such behaviors can be “bad behaviors”, leading to goal conflicts when
aiming for improved welfare. Aggressive behavior has a genetic background,
as described above. To attack a foreign pig could be regarded as a normal
behavior in confined situations where contact cannot be avoided. The conse-
quence of the freedom to express such behavior has only been studied from
one perspective, i.e. the perspective of the attacked pig whose welfare is
decreased. Whether having the freedom to express an aggressive behavior is
related to higher welfare has not been studied. Assessment of positive emo-
tions in animals is a complex but growing research field ( Boissy et al.,
2007 ).
One example of a normal or natural behavior is mounting. Mounting is
more frequent in entire males than castrates and females, but the entire males
seem to mount other pigs regardless of sex ( Rydhmer et al., 2006 ).
According to Hemsworth and Tilbrook (2007) there are breed differences in
male sexual behavior and the heterosis observed for libido in crossbred males
also indicates a genetic background. In boars used for mating or for semen
collection, sexual behavior is, of course, a wanted behavior. In entire males
raised for slaughter, on the contrary, mounting is an unwanted behavior.
Excessive mounting leads to injuries ( Rydhmer et al., 2006 ). It would proba-
bly be possible to decrease the frequency of mounting by selection, but
selection against sexual behavior can hardly be included in any breeding pro-
gram claiming to be sustainable in a long-term perspective.

CONCLUDING REMARKS
As this review has shown, many behavioral traits important for welfare are
heritable and could thus be modified by selection. Furthermore, the ongoing
selection for high production seems to influence pigs' behavior. For example,
selection for leaner pigs is risky since it increases reactivity to stressors, and
should not be done without monitoring pig behavior (as well as health and
reproduction). The responses to both acute and chronic stressors need to be
considered when analyzing the capacity of an animal to adapt behaviorally
to the environment, because they refer

to different mechanisms of

adaptation.
The lowest welfare in pig production is probably found among
growing

finishing pigs kept indoors. These animals live in an environment
that is extremely boring, especially for such an explorative animal as the pig.
Are pigs too smart for their own good? George Orwell knew about pigs'
mental capacity when he wrote Animal Farm: “The work of teaching and
organizing fell naturally upon the pigs, who were generally recognized as