Agriculture Reference
In-Depth Information
3.1
Introduction
World-wide individual dry sows housing systems are gradually replaced by group
housing systems. The European Union has banned individual housing of sows from day
28 of pregnancy onwards (EU, 2008), in a number of US states group housing has been
made compulsory (Harris, 2014), and in Australia and New Zealand legislation also
includes the requirement to group house pregnant sows (Harris, 2014). However, the
actual conversion of individual to group housing does not proceed rapidly: the Humane
Society International (HSI) reported on January 1
st
2013 (the time at which the European
ban officially came into force) that 14 pig producing member states of the European
Union still failed to meet the legislation. Many farmers delayed conversion to the very
last moment for various reasons primarily related to the cost of investment and the lack
of confidence in the system (Tuyttens
et al.
, 2011).
The scientific debate regarding relative merits is fuelled by evidence either in favour or
against group housing as an alternative to individual housing of pregnant sows. One of
the first major protagonists of group housing was the European Scientific Veterinary
Committee which, in 1997, published their scientific report on the wellbeing of intensively
kept pigs (SVC, 1997). Their view was challenged, however, by Australian scientists a few
years later (Barnett
et al.
, 2001). The problem that science has to reach a consensus was
highlighted by the American Veterinary Medical Association. In their 2005 report they
avoided having to recommend either group housing or stalled systems by concluding that
'The immediate need is for industry to advance housing and management practices in
ways that will improve the welfare of sows while providing producers with practical and
reliable methods' (Rhodes
et al.
, 2005).
Research into the relative merits of group housing versus individual housing has not
made much progress since. Jansen
et al.
(2007) confirmed that group-housed sows were
involved in more aggressive encounters than stall-housed animals, and that there was no
effect of housing on backfat depth or sow fertility. Harris
et al.
(2006) agreed that there
were few differences in productivity between gilts housed for one pregnancy in groups
of four or in stalls. Reproductive performance, for example, did not differ (even though
levels of aggression obviously did). Karlen
et al.
(2007) found that sows in large groups
on deep litter faced greater welfare challenges in the early stages of gestation, based on an
increased incidence of scratches, a higher rate of return to oestrus and a trend for greater
cortisol concentrations early in gestation. All these factors are possibly a consequence of
aggression. In contrast, sows in stalls faced greater welfare challenges later in gestation
as indicated by a higher incidence of lameness and an increased neutrophil: lymphocyte
ratio, being perhaps a consequence of increased stress. In conclusion, these data suggest
that in both housing systems the welfare advantages and disadvantages change over time.
Finally, Chapinal
et al.
(2010) confirmed that stereotypic behaviours are less prevalent
in group-housing systems whereas vulva lesions and lameness are more prevalent. They
conclude that a higher quality of stockmanship may be required in group-housing systems
to detect problems and maintain a similar level of productivity and tissue damage than
in individual housing.
