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.