Genetics and Animal Welfare - Genetics and the Behavior of Domestic Animals - page 435

pigs. Pigs could manipulate the straw even while lying down. Age may also
influence aggression and tail biting. Li et al. (2012) suggest that young sows
are vulnerable in group-gestation systems when mixed with mature sows.
Sorting sows by the number of times they have given birth improves welfare
and performance by reducing severe injuries and fighting.
Savaging in Sows
Sows killing their piglets is an example of an extreme welfare problem that
may interact with environmental conditions. Sows that savage are more rest-
less at farrowing. Ahlstrom et al. (2002) suggest that aberrant maternal
behavior during farrowing or an individual's inability to cope with restrictive
environments may be contributing factors in savaging. Chen et al. (2008)
compared behaviors such as grinding teeth, rearing, lying down with care,
and prepartum nest-building behaviors. These behaviors were not a predictor
of savaging. However, Chen et al. (2008) reported that sows that made more
postured changes during farrowing were more likely to savage. This suggests
that savaging is part of a more generalized behavioral pathology that
includes increased excitability—not specifically piglet directed. Baxter et al.
(2011) found that modifying the farrowing environment affected maternal
behavior in sows, and suggest that it is essential to evaluate sows in the envi-
ronment they will be housed in. This is especially important when sows from
different genetic lines are being switched from indoor, intensive environments
to outdoor environments. Sows attacking and killing their own newborn
offspring is a serious welfare concern that requires further study.
Feather Pecking in Hens
In the egg-production sector, feather pecking is a serious welfare and eco-
nomic problem. Several recent studies have focused on behaviors of genetic
lines of hens selected for either high or low feather pecking. Evidence
suggests that feather pecking in laying hens may be misdirected foraging
behavior. Rodenburg et al. (2010) investigated the underlying motivation of
feather pecking in genetic lines of chickens bred for high and low feather
pecking. Results suggests that fear may not be the primary motivator, since
the two genetic lines had similar reactions on the novel object test and
human-approach test ( Rodenburg et al., 2010 ). It has also been suggested
that dietary factors could play a role in feather pecking, however, hens
selected for high feather pecking ate more of a high-fiber diet ( Kalmendal
and Bessei, 2012 ). Lines selected for increased feather pecking showed
increased motivation for locomotor activity ( Kjaer, 2009 ). de Haas et al.
(2010) found that a high feather-pecking line ate worms faster. This is further
evidence that feather pecking is displaced foraging. High-producing animals
require vast quantities of food. The first author speculates that selection for high