ABSTRACT Farm animal welfare is a major issue in
Europe, which resulted in regulations and development
of research dedicated to animal welfare, especially on
standard poultry production, which is often considered
as resulting in very poor welfare. The effect of selection
is also often questioned. Indeed, capacities of adaptation
have been very little considered during the first
years of commercial selection and thus have been reduced.
Nowadays, a much greater importance is given
to welfare-related traits and genomic selection should
alleviate the need for their measurements in the shortterm.
However, the choice of the fittest selection criteria
is still to be made. Because behavioral traits are highly
dependent on environment, general reactivity may be
more efficient. For example, selection against undesirable
behavior such as feather pecking has been proven
to be efficient, but selection for reduced mortality rates
in collective cages proved to be preferable. Most often,
selection should not exacerbate extreme values, which
are most often detrimental, as in the case of social motivation,
which, when increased to too large of an extent,
results in increased aggressivity. Moreover, a general
propensity will not result in overall improvement; for
example, reducing fearfulness has positive effects but
does not modify response to social stress. Detrimental
effects on other traits may also be observed: although
genetic resistance to diseases should increase animal
welfare, it may also result in increased frequency of silent
carriers and in turn to human transmission. Indeed,
an optimum must be found. Studying lines selected for
or against these traits will be of great help to choose
the best strategy of selection. Another and longer term
concern should be on links with other production traits
but also on sustainability, which will probably be of
greater importance in the coming years.