2. Materials and methods
2.1. Animals, housing and feeding
The experiment was conducted at a commercial farm
located in the west of Jutland, Denmark, during spring
2005. The experiment included 36 pens; 12 positioned in
building one and 24 positioned in an identical building
(building two). All pens measured 2.35m 4.7m and had
concrete floor (2/3 solid and 1/3 slatted). The experimental
animals were weaned at an average of 5 weeks of age and
moved to the pens immediately after weaning. The first 5
weeks after weaning the pigs were floor fed a dry food five
times daily during the period from 07.00 h to 22.00 h. After
that a commercial dry food was offered ad libitum via tube
feeders (TUBE-O-MAT, Egebjerg Maskinfabrik A/S, Esbjerg,
Denmark) while the frequency of floor feeding was
gradually reduced to zero over a 3-week period. All
management procedures were conducted between 09.00
and 10.30 h, and outside this period the pigs were left
undisturbed. From weaning until the experimental period
started, pigs were given chopped straw as rooting material
twice a week.
2.2. Experimental treatments
When the pigs of a block were approximately 30 kg live
weight the pens were assigned to one of four treatments:
(1) low space allowance and maize silage as rooting
material, (2) high space allowance and maize silage as
rooting material, (3) low space allowance and straw as
rooting material, or (4) high space allowance and straw as
rooting material. The two space allowances were achieved
by adjusting the group size to 17 or 11 pigs per group
yielding a space allowance of either 0.64 or 1.0m2/pig. The
experimental pigs were selected to achieve a weight
homogeneous group composition and an average start
weight within the group of 30 kg. The volume of the two
materials offered was the same, approx. 3.8 l/pig. The
corresponding weight was approx. 350 g of maize silage
per pig per day and approx. 90 g of chopped straw per pig
per day. Within building the four treatments were
balanced across location and each treatment was repeated
three times in building one and six times in building two.
Rooting material was allocated daily. Pens were allocated
the material in the same order and the allocation started at
10.00 h.