Agriculture Reference
In-Depth Information
keeping their feeding and lying areas free from manure and urine. They will find a place
in the pen which is most comfortable to lie in. Aspects that determine the quality of
the lying area are that it should be away from the main activity in the pen (such as
walkways, feeders and drinkers), dry, draft free and providing protection from nosey
neighbours (e.g. by solid pen partitions). The dunging area is generally positioned not
too far away from the lying area in a quiet place with a good foothold, so that the animal
can comfortably arch its back. Pigs keep their lying area and themselves clean, and will
only lie in their own excrement when they are no longer able to cool their body, e.g. due
to high ambient temperatures.
The design of the pen may also be relevant in relation with social behaviour of the sows.
Docking
et al.
(2000) concluded that a circular pen with a large space allowance (in their
case 9.3 m/sow, with groups of 5 unfamiliar sows) is best to reduce aggression. However,
for an optimal combination of escape possibilities and cost for building a pen, rectangular
pens at low stocking densities with hiding areas were advised.
Effects of climate on performance and behaviour
Changes in temperature, humidity and light will affect sow behaviour and reproductive
performance. Group housing is identified as a risk factor for seasonal infertility
(Peltoniemi and Virolainen, 2005; Peltoniemi
et al.
, 2000). The most obvious sign of
seasonal infertility is the so-called 'autumn rebreeding': the seasonal increase in sows
that return to oestrus between d 25-30 after insemination. The cause of this phenomenon
seems to lie in the suppression of GnRH/LH release resulting from increased melatonin
concentrations. Melatonin is produced by the pineal gland during the dark period of the
day, and thus normally increases in autumn. Indeed, infusion of melatonin negatively
affects farrowing rate (Love
et al.
, 1993). Further, during an autumn photoperiod, LH
concentrations are decreased (Peacock, 1991; Love
et al.
, 1993), thereby resulting in lower
progesterone concentrations from approximately d 14 of pregnancy onwards (because
from that moment on, progesterone production is dependent on LH levels). These lower
progesterone concentrations induce delayed embryo development, resulting in regression
of the
corpora lutea
and return to oestrus. Sows with a low feed intake during early
pregnancy seem especially vulnerable. Geudeke and Gerritsen (2004) also showed that
the phenomenon of autumn rebreeders had a greater occurrence on farms with group
housing of pregnant sows, and was also related to the average body condition of sows and
to the quality of the indoor climate.
The behaviour of pigs is also strongly related to aspects of temperature and ventilation in
the pen. As discussed above, poor climatic circumstances (high temperatures) will result
in sows lying in their faeces to cool down. Drafts and other aspects of the climate which
disturb sow resting behaviour may result in increased interactions between animals and
in negative performance of the group.
