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

- How does group housing vary in practice? -
From weaning until four weeks after mating, individual feeding procedures are preferred,
however, systems with group feeding procedures in the entire non-lactating period do also
exist (Sørensen & Thorup, 2003; pers. comm. Hansen, 2004, own observations).
Group dynamic/group size
A group of non-lactating sows may either be stable or dynamic. In stable groups, once the
group is established no new sows are moved into the group. In dynamics groups, new sows
are constantly moved into and out of the group e.g. up till once a week (Svendsen et al.,
1990). Group sizes may vary from 2 (Deininger, 1998) to 150 (Nielsen et al., 2000) sows
per group. In the service unit the groups are often stable with group sizes equal to or less (if
division into smaller groups take place at weaning) than the size of the farrowing batch.
Mixing of unfamiliar sows
Frequently, sows are individually housed in the lactating unit why sows usually are mixed
with unfamiliar sows when moved from the lactation unit to the service unit (Edwards,
1992; Deininger, 1998). In some herds the service and pregnancy units are integrated. In
these systems sows stay in the same pen from weaning to shortly before farrowing. In many
herds, however, sows are relocated at least once more when moved from the mating to the
pregnancy section. This may happen in from a few hours to three-four weeks (own observations)
after insemination.
Stocking rate
Stocking rates from less than 2 m 2 (Mortensen & Ruby, 1990; Deininger, 1998) to more
than 4 m 2 per sow (Svendsen et al., 1990) or even 5 m 2 per sow (Deininger, 1998) are practised.
Often, the stocking rate in the service unit is less compared to the stocking rate in the
pregnancy unit (pers comm., Hansen 2004) because it is believed that a high stocking rate
in this period may influence reproduction negatively.
Floor type
Systems exists with large ‘open’ floor plan with deep straw bedding, however, the floor
may also be divided into a lying/activity and a dunging area (Olsson et al., 1991). The
dunging area may consist of slatted or concrete floor. The lying/activity area may consist of
concrete with or without small amounts of straw provided, straw bedding or deep straw
bedding (Deininger, 1998). It is common to use some amount of straw in the service unit
because it is believed to minimize the risk of leg injuries caused by fighting and mounting
during oestrus (Hansen & Kongsted, 2002). Depending upon the system in use, the amount
of straw provided may vary from zero (own observations) to 1.000 kg per sow per year
(Svendsen et al., 1990). The lying/activity area may be divided into smaller or larger ‘nests’
by means of ‘pen dividers’ as shown in picture 3.
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