Reproduction performances and conditions of group-housed non ...

- Background and aim -
BACKGROUND AND AIM
For several decades, individual housing of non-lactating sows was preferred, probably because
individual housing made it possible to control the individual sows access to important
resources like feed and water. However, in the last decade the number of group housed nonlactating
sows has begun to increase in Europe. This is mainly caused by elevated public
concern of animal welfare with changed legislations as a consequence. For instance, according
to EU legislation all sows have, from January 2013, to be loose-housed in smaller
or larger groups from four weeks after mating until seven days before expected farrowing
(Council Directive 2001/88/EC amending Directive 91/630/EEC Laying Down Minimum
Standards for the Protection of Pigs). In addition, national extraordinary laws have been
introduced in several countries. In England, for instance, all sows have to be group housed
in the entire period from weaning to seven days before expected farrowing according to the
national legislation (The welfare of Farmed Animals (England) (Amendment) Regulations
2003). In Norway, the sows may only be fixed from three days before until one week after
farrowing, and in Sweden it is only allowed to keep sows in crates for maximum one week
if necessary during the production cyclus (Baustad & Lium, 2002). Although no laws or
regulations so far, similar tendencies are also seen in other parts of the world (McGlone,
2001; Trezona, 2003).
In Denmark it is still legal to keep the sows in crates from weaning until four weeks after
mating. Nevertheless, the Danish Bacon and Meat Council, motivated by export interests,
has introduced an extra pay for slaughter pigs produced by sows that are group housed in
the entire non-lactating period. This additional price has caused an increase in the number
of sows that are group housed from weaning to shortly before farrowing in Denmark.
However, impaired reproduction in form of reduced litter size and pregnancy rate in group
housed compared to individual housed sows in parts of or in the entire non-lactating period
has been observed in several Danish on-farm experiments. Sows group housed from weaning
until two days after mating had significant fewer total born piglets compared to sows
individually housed in the same period (Hansen, 2000). Sows group housed from weaning
to farrowing had significant fewer total born piglets per litter than sows kept individually in
crates the first four weeks after weaning and thereafter loose housed until farrowing
(Fisker, 1995). Equally, in other countries a reduced farrowing rate has been seen in group
housed compared to individual housed sows (USA: Hurtgen et al., 1980; Finland:
Peltoniemi et al., 1999). Conversely, in other studies, no difference (conception rate and
litter size: England & Spurr, 1969) between grouped and individually housed sows or even
opposite effects (farrowing rate: Bates et al., 2003; Hansen, 2003) have been found. The
divergent results are probably a result of differences in the function of the group housing
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