In a further step in the definition of welfare, Duncan
and Fraser (1997) stated that qualifying animals
as sensitive beings involves taking in account their affective
state. Thus, they recommend to avoid, as much
as possible, negative emotions such as fear, pain, or
frustration and to enhance positive emotions. Indeed,
assessing the presence and nature of emotion is still
questionable, but current research should make it possible
in the future (Boissy et al., 2007).
Finally, the natural approach implies letting the animals
express their natural behaviors. From these viewpoints,
some physical suffering or even predation may
be acceptable as natural events.
The relative importance of these 4 positions is an important
ethical and economic issue, which is still under
question. Considering all of them, the Farm Animal
Welfare Council defined 5 freedoms for animals (Farm