The amount of rooting material offered is also an
issue. Day et al. (2002) found that the time spent
manipulating straw was increased by increasing the
amount of material allocated, and that increasing the
amount of straw resulted in a concurrent lowering of
manipulation of pen mates. However, the amount
available varies over the 24 h as material that is allocated
once a day is used up (eaten, soiled or lost in the manure)
to such an extent that there may be no material left just
before the next allocation. Therefore, it is relevant to
investigate pigs’ interaction with material in relation to
time of allocation.