Behavioral Genetics in Pigs and Relations to Welfare - Genetics and the Behavior of Domestic Animals - page 398

very large litter for being such a large animal. At the approach of farrowing,
the pregnant sow becomes intolerant of group mates ( Stolba and Wood-
Gush, 1989 ). In the wild, the sow leaves the group 3 days before
farrowing and searches for a suitable site where she builds a nest with
materials from the vegetation. In the farrowing stable, the sow also builds
a nest if given building material and space. Sows spend around 15 hours
on nest-building activities ( Thodberg et al., 1999 ) and in the absence of
material, sows direct their activity at the floor, walls, and bars ( Wischner
et al., 2009 ). They humidify the floor with their snout and paw insis-
tently with their front legs. The nest-building activities are very similar
in wild boar sows and domestic sows housed indoors ( Stolba and Wood-
Gush, 1989 ).
When the first piglet is born the sow reduces the number of postural
changes and lies still until most piglets are born. The farrowing takes on
average 4 hours ( Wallenbeck et al., 2009 ). Sows differ in their maternal
skills, which influence the probability of survival of the piglets. Before
lying down, some sows carefully check if there are any piglets, in order
to avoid crushing them. Others do what Wechsler and Hegglin (1997)
describe as “flopping straight down” which is a great risk for the piglets.
An attentive sow reacts to piglet screams by changing posture and thus
many piglets are saved. Sows' reactions to the sound of screaming piglets
have been used as a measurement of maternal behavior ( Grandinson
et al., 2003 ). Unlike the ewe, the sow does not lick her young. Instead,
the piglets initiate frequent nose-to-nose contact with their mother. Most
sows can bond to alien piglets, which is convenient

in high-producing

herds since it allows cross-fostering as a means to optimize piglet

survival.
The nursing is based on a sophisticated interaction between the sow and
its piglets ( Canario, 2006 ). After vigorous competition among littermates
during the first days, each piglet gets its own teat. The sow nurses the piglets
every hour, day and night. She initiates the nursing event by grunting and
lying down on her side. The piglets respond by massaging the udder for
a few minutes, which stimulates oxytocin release resulting in the milk
let-down. After the milk ejection, which is around 20 seconds, the piglets
continue to massage the udder until the sow interrupts nursing by standing
up or rolling on her belly, or until the piglets leave the udder or fall asleep.
The total nursing event takes, on average, 5 minutes but the variation is large
( Wallenbeck et al., 2008 ).

FAWC'S FIVE FREEDOMS
The Farm Animal Welfare Council's definition of animal welfare ( FAWC,
1992 ) lists five freedoms. These freedoms define ideal states and form a
comprehensive framework for analysis and discussions of animal welfare