Jensen, M. B., Studnitz, M., Pedersen, L. J. 2010. The effect of type of rooting material and space allowance on exploration and abnormal behaviour in growing pigs. Applied Animal Behaviour Science 123(3-4), 87-92.

The experiment aimed to investigate the effect of type of rooting material and space allowance on explorative and abnormal behaviour in growing pigs. Thirty-six pens with partly slatted concrete floor were allocated 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, and (4) high space allowance and straw as rooting material. Pens with low space allowance had 17 pigs (0.64 m2/pig), while pens with high space allowance had 11 pigs (1.0 m2/pig). Behaviour was recorded by instantaneous sampling during 1 h before and 1 h after the daily allocation of rooting material at 10.00 h, as well as during 1 h in the afternoon starting at 13.00 h. Observations were conducted at 13 and 20 weeks of age. Pigs offered maize silage manipulated rooting material more (23% vs. 19% of the pigs; P < 0.001) and manipulated pen components less (3.3% vs. 4.5% of pigs; P < 0.01) than pigs offered straw. Pigs housed at a high space allowance manipulated rooting material more (22% vs. 19% of pigs; P < 0.05) than pigs at a low space allowance. At 13 weeks of age, pigs manipulated rooting material more (23% vs. 18% of pigs; P < 0.001), pen components more (4.8% vs. 3.1% of pigs; P < 0.01) and pen mates less (2.2% vs. 3.0% of the pigs; P < 0.05) than at 20 weeks of age. Manipulation of rooting material was lower before the daily allocation of rooting material than after (15%, 40% and 7% of pigs at 09.00, 10.00 and 13.00 h, respectively; P < 0.001), while manipulation of pen components (6.4%, 3.5% and 1.9% of pigs at 09.00, 10.00 and 13.00 h, respectively; P < 0.001) and pen mates (4.1%, 2.1% and 1.5% of the pigs at 09.00, 10.00 and 13.00 h, respectively; P < 0.001) were higher before allocation of rooting material than after. In conclusion, pigs manipulated maize silage more than chopped straw and the level of explorative behaviour redirected towards pen components was lower when maize silage was offered as a rooting material. Pigs with a high space allowance manipulated the rooting material more. Finally, increased manipulation of pen mates and pen components just before allocation of new rooting material suggest that the amount available just before the next allocation was insufficient to maintain material manipulation.