Behavioral Genetics in Pigs and Relations to Welfare - Genetics and the Behavior of Domestic Animals - page 410

nucleus herd of 100 sows, approximately 12 sows are weaned every third
week. One hour's work every third week would allow the farmer to mark the
sows and record aggressive behavior and then the breeding organization
could include aggressive behavior of sows in the genetic evaluation and
select against it, in order to improve welfare. Hellbr¨gge et al. (2008)
recorded aggressive behavior of pregnant sows when mixed in small groups
during washing, before entering the farrowing unit. Eighteen per cent of the
sows were aggressive and the heritability was estimated with a threshold
model at 0.3. They also found favorable genetic correlations between aggres-
sion in groups and maternal behavior (less aggressive

stronger reaction to

the sound of a screaming piglet).
Marker-assisted selection is proposed as a method of decreasing aggres-
sion in pigs. Several markers and some genes governing aggressiveness have
been found in rodents and with a candidate gene approach based on genes
with a known impact on the hypothalamic

adrenal (HPA)
axis, associations between skin lesions and the gene NR3C coding for a glu-
cocorticoid receptor as well as the gene AVPR1B coding for a vasopressin
receptor were found in pigs ( Mur ´ ni et al., 2010 ). Terenina et al. (2012)
used the same data set and found markers indicating that both dopamine-
and serotonin-related genes are involved in the genetic variation of
aggressiveness.

pituitary

Maternal Behavior
Piglet mortality is a severe problem in pig production related to the ongoing
selection for larger litters and leanness. Genetic studies on behavior of new-
born piglets are scarce, but several genetic studies on maternal behavior have
been performed. The long-term goal of most of these studies is to decrease
piglet mortality by breeding. The International Coalition for Animal Welfare
(ICFAW) represents non-governmental animal welfare organizations from all
over

the world and contributes to the decision-making at the World

Organisation for Animal Health (OIE). ICFAW recommends:

Selective breeding should focus on improving the welfare of pigs by selecting for,
e.g., breeds which make good mothers and are less likely to crush their young,
smaller litters of healthier, more robust piglets and resistance to stress and disease.
( ICFAW, 2010 )

Maternal behavior starts already before farrowing, with nest building.
This behavior makes the sow different from other ungulates. Nowak et al.
(2000) wrote “The fact that nest building has been retained in spite of
domestication indicates how robust this maternal behaviour is.” Nest build-
ing is performed to provide the piglets with shelter and comfort, and particu-
larly to keep them warm. This is especially important for small piglets due