Ž . straw and branches would terminate nest building sooner and 3 they would be calmer
during parturition than gilts with access to straw only.
2. Materials and methods
2.1. Animals, housing and care Forty-two primiparous Danish Landrace Yorkshire crossbred sows were used. During
gestation the animals were housed in stalls, in which they had access to cut straw. By random selection the gilts were designated to either an experimental group with straw
and branches or a control group with only straw. Five to seven days prior to the Ž
. expected date of parturition the gilts were moved to individual farrowing pens Fig. 1
which were situated in the same room. The pens were designed to stimulate and allow Ž
. natural nest-building behaviour Schmid, 1991, 1993 . A 2.6 = 2.7 m pen was divided
Ž
2
. into a resting area 2.86 m
covered by 20 kg of long cut straw and a solid floor Ž
2
. activity area 4.16 m . A piglet box was situated in the centre of the pen. A nipple
drinker, a feed trough, a straw rack and a branch rack were placed in the activity area. The racks were filled regularly and the gilts thus had unlimited access to nest building
material. The materials were bare branches of 2–4 cm in diameter and 40–75 cm in
Ž .
Ž .
length experimental group and long cut straw experimental and control group . The gilts were fed standard sow rations twice daily. If, however, nest building was
apparently terminated and parturition was pre-eminent the ration was withheld until 2 h Ž
. after birth of the first piglet BFP . This was done to prevent disturbance of gilts, which
had possibly completed nest building and might remain in their nests if undisturbed. The
Ž Fig. 1. Schematic drawing of the farrowing pen, which is slightly modified form the design of Schmid 1991,
. Ž
. 1993 . In the experimental group ns 21 both straw and branch racks were filled regularly. In the control
Ž .
group ns 21 only the straw rack was filled.
activity area was cleaned daily and the straw-bedded area was cleaned if soiled. When Ž
signs of nest building nest building behaviour, materials removed from the racks or .
materials arranged in the resting area had been observed the pen was no longer entered. Room temperature was kept at 17 38C and recorded every morning throughout the
experiment. The room was ventilated by fans and lit both by natural daylight and artificial lighting switched on at 07.00 h and off at 15.00 h. At all hours infrared lamps
switched on automatically when light became too dim for video recording to take place.
2.2. BehaÕioural obserÕations The gilts were video recorded from day 113 in gestation until parturition was
Ž .
completed using 24 h time lapse recording three frames per second . The period from 24 h prior to BFP until 2 h after BFP was observed and analysed.
2.2.1. Prepartum nest building behaÕiour For all gilts it was recorded whether the provided materials were used for nest
building during the last 24 h prior to BFP. The criterion for use of materials was that the gilt collected and arranged straw or both straw and branches when these were provided.
Furthermore, the time of termination of nest building was recorded. The prepartum phase was divided into 5-min intervals. Termination of nest building was then defined as
the end of the last 5-min interval in which rooting had occurred in more than two successive intervals or the end of the last interval in which collecting or arranging straw
or branches had been performed.
In order to describe the use of branches, 10 gilts were selected randomly from the experimental group. Detailed behavioural analysis was carried out from 24 h prior to
parturition until 2 h after BFP. Nest building was recorded by onerzero sampling in 5-min
intervals. The
behaviours recorded
were rooting,
pawing, collecting
strawrbranches, arranging strawrbranches, and biting the pen equipment. 2.2.2. Parturient behaÕiour
For all gilts it was recorded whether or not nest building occurred during the first 2 h of parturition. Nest building during parturition was defined as occurrence of pawing,
collecting or arranging straw or at least 4 min of standing in the nest rooting. The 4-min criterion was chosen on the basis of observations from semi-natural environment
Ž .
Petersen et al., 1990 . Here sows were observed to get up to sniff their piglets during farrowing, but this usually lasted less than 1 min and never more than 3 min.
Additionally, number of minutes spent in lateral recumbency with the udder exposed and number of postural changes were recorded. Number of postural changes included all
changes between lying, sitting and standing. Definitions of nest building behaviours can be seen in Table 1.
2.3. Statistical methods When analyses which require normality of data were used, the distribution was tested
Ž .
using Proc Univariate of SAS Delwiche and Slaughter, 1995 . The interval from
Table 1 Behaviour recorded by 1r0 sampling in 5-min intervals in 10 gilts with branches from 24 h prepartum until 2
h after BFP Behaviour
Definition Rooting
Snout movements directed at the straw bedding or at branches in the bedding Pawing
Moving a foreleg back and forth in the straw bedding Collecting straw
Taking straw from the rack or floor and carrying it in the mouth while taking at least two steps
Collecting branches Taking branches from the rack or floor and carrying it in the mouth while taking
at least two steps Arranging straw
All other straw-directed behaviour than rooting and collecting straw that occurred in the resting area
Arranging branches All other branch-directed behaviour than rooting and collecting branches that
occurred in the resting area Biting pen equipment
Biting and chewing pen equipment
termination of nest building to BFP in gilts with branches and gilts with no branches was compared by survival analysis using a Log-Rank test in the Proc Lifetest of SAS
Ž .
Allison, 1995 . The association between provision of branches and frequency of animals performing nest building during parturition was analysed by a x
2
test in the Ž
. Proc Freq of SAS Delwiche and Slaughter, 1995 . Wilcoxon 2-sample tests using the
Ž .
Ž . Proc Npar1way of SAS 1989 were carried out to compare the 1 number of postural
Ž . changes and time spent in lateral recumbency between the two treatment groups, 2
number of postural changes and time spent in lateral recumbency between gilts that did Ž .
perform nest building during parturition and gilts that did not, and 3
the room temperatures for the two treatment groups. Use of branches and straw in the 10 gilts that
were studied in detail was analysed by paired t-tests using the Proc Means of SAS Ž
. Delwiche and Slaughter, 1995 .
3. Results
