Agriculture Reference
In-Depth Information
lying k=0.047. It can be calculated that for a 200 kg sow this equates to 0.65 and 1.61 m
2
for sternal and recumbent lying, respectively. Although data on the behavioural space
needed by sows for such behaviours as feeding and dunging are lacking, these can be
estimated on the basis of the posture and the number of animals involved. The space
required to get access to the area were the behaviour takes place is of course also relevant.
Space requirements where interactions take place, for e.g. mating, fighting and fleeing,
are the most difficult to estimate. Baxter (1985) estimated the amount of space sows need
when engaging in a two-sided fight to be 0.11×W
0.667
. This equates to 3.8 m
2
for a fight
between two 200 kg sows. What makes an estimation of spatial need complicated is that it
depends on the frequency of occurrence and the level of concurrence in a group of sows.
Fleeing to escape from aggression may involve flight distances from below 2.5 m up to
incidences where sows were pursued for over 20 m (Edwards and Riley, 1986; Kay
et al.
,
1999). What is relevant to note is that the space requirements for social interactions have
a temporary nature. Both mating and fighting for dominance are temporary activities and
the space required for these should be offered in specialised mixing pens or mating areas
There are several studies which looked at the effects of different space allowances on
performance and aggression. Barnett
et al.
(2001) suggested space allowances of 1.4-1.8
m
2
for optimal production performances, although they also quoted literature suggesting
that 3 m
2
per sow provides better reproductive results compared with 2 m
2
. Weng
et al.
(1998) looked at the effects of 2.0, 2.4, 3.6 and 4.8 m
2
per animal on aggression and skin
lesions and concluded that for stable groups of 6 sows fed separately in stalls, the minimum
recommended space allowance is between 2.4 and 3.6 m
2
per animal. They stress that
this result should not be generalised to other group sizes or feeding systems because it is
possible that in larger groups the amount of space required may be less. Salak-Johnson
et
al.
(2012) also compared different floor space allowances (1.4, 2.3 and 3.3 m
2
) for small
groups of 5 sows, and found that although the frequency of aggressive interactions was
not significantly different, sows on 3.3 m
2
were engaged for longer aggressive interactions
compared with sows on 1.4 m
2
. Unfortunately, there was no comparison of lesions
scores in this study. In earlier work from the same group, comparing the same stocking
densities (Salak-Johnson
et al.
, 2007), there was a decrease in lesions with increasing
space allowance, which is more in line with what other studies indicate. The apparently
contradictory results in 2012 may therefore be associated with a lower intensity per
incident of the interactions at increased space allowances. Finally, Hemsworth
et al.
(2013)
also confirmed that, based on aggression and cortisol results, sow welfare improves when
comparing increased space allowances from 1.4, 1.8, 2.0, 2.2, 2.4 to 3.0 m
2
. They indicated
that they could not determine what is an adequate space allowance for sows, although they
confirmed that a space allowance of 1.4 m
2
/sow is too small.
Group size
Various group sizes have been investigated in relation to aggression and performance.
Barnett
et al.
(1986) compared levels of aggression in groups of 2, 4 and 8 sows and
found no significant differences in aggression (nor in reproduction variables). Later
work concluded that sows in larger groups with a larger and more varied space generally
