Behavioral Genetics in Pigs and Relations to Welfare - Genetics and the Behavior of Domestic Animals - page 399

within the proper constraints of an effective pig production unit. The five
freedoms are:

Freedom from hunger and thirst—by ready access to fresh water and a
diet to maintain full health and vigor.
Freedom from discomfort—by providing an appropriate environment
including shelter and a comfortable resting area.
Freedom from pain, injury, or disease—by prevention or rapid diagnosis
and treatment.
Freedom from fear and distress—by ensuring conditions and treatment
which avoid mental suffering.
Freedom to express normal behavior—by providing sufficient space,
proper facilities, and company of the animal's own kind.

Although these freedoms, as stated by FAWC, do not refer directly to
genetics and breeding, we use them as a structure for this chapter.

FREEDOM FROM HUNGER AND THIRST
Are hunger and thirst welfare problems for pigs? In many countries, young
pigs during the growing finishing phase as well as lactating sows are given

ad libitum access to feed and water. There is sometimes competition between
pen mates at the feeder or water nipple. Such competition is, however, prob-
ably more related to “fear and distress” or “discomfort” than to “hunger and
thirst”.
Some newborn piglets do, in fact, starve, and most piglets have a
restricted access to milk. A piglet ingests around 40 g of milk per meal and
the piglet's total milk intake can be estimated as 25% of the increase in body
weight ( Noblet and Etienne, 1989 ). Piglets have a very high capacity to eat
(or rather to drink) and it is not known whether the difference between milk
intake capacity and realized milk intake is related to hunger, but piglets
starving to death are of course a welfare issue. Piglet mortality and growth
are governed by both the genes of the sow and the genes of the piglet
( Grandinson, 2003 ). Sows' milk production (recorded as litter growth) also
has a genetic background ( Lundgren, 2011 ).
A lactating sow producing as much as 15 liters of milk per day cannot
eat enough to fulfill its nutritional needs during lactation. One way to over-
come this restriction and increase milk production could be to select for
increased appetite or voluntary feed intake during lactation. Pig breeders sel-
dom think of appetite as a behavioral trait, but in humans food intake is often
discussed in relation to behavior. Selection for increased voluntary feed
intake of lactating sows was proposed by Eissen et al. (2000) . Problems with
low appetite increase with increasing temperature. Bergsma and Hermesch
(2012) have recently shown that breeding for reduced thermal sensitivity of
feed intake is possible. Lundgren et al. (2013) found genetic correlations