Influence of the accessibility of straw in racks on exploratory behaviour in finishing pigs

To safeguard the welfare of finishing pigs, known for their strong motivation to explore, provision of an adequate quantity of enrichment material is important. The aim of this study was to examine the effect of the accessibility of straw provided in racks on exploratory behaviour in pigs. Two hundred and sixteen finishing pigs with undocked tails were housed in eight groups of 27 pigs each for 12 weeks. They were kept in pens with a partly slatted floor and access to an outdoor area and were fed with liquid feed twice daily. To vary accessibility of enrichment material the number of filled straw racks (one, three, six or eight) provided in a pen was changed in each group every 21 days using a cross-over Latin square design. Video recordings were made for 16.5 h on the 2nd and 18th day after changing the number of filled racks. The number of pigs showing exploratory behaviour towards the racks (exploring filled rack) as well as towards straw which dropped from the racks onto the lying area (exploring straw on the floor) was recorded by 10 min scan sampling. Displacements from the racks were recorded continuously. Data were analysed using linear mixed-effects models. Exploratory behaviour followed a daily biperiodical pattern with the highest levels recorded 3 h after morning feeding (7:00-10:00 h) and about 2 h before and after feeding in the afternoon (14:30-19:00 h). The proportion of pigs per scan exploring filled racks (p < 0.001) as well as exploring straw on the floor (p < 0.007) increased monotonically as the number of filled racks increased. The rate of displacements from the rack tended to decrease monotonically with an increasing number of racks (p=0.083). It seems that provision of more enrichment material increasingly stimulates the exploratory behaviour of finishing pigs at least up to 19 cm rack space per pig. (C) 2012 Elsevier B.V. All rights reserved.