Anticipation of a food ball increases short-term activity levels in growing pigs

Analogous to the way in which repeated episodes of stress can lead to a negative emotional state, it is possible that repeated positive emotions could lead to a positive emotional state. Positive emotions can be induced by providing enrichment or by successfully coping with cognitive challenges. The aim of this study was to determine whether limited access to a ball filled with corn is a suitable enrichment for growing pigs and whether they learn to anticipate the enrichment after an acoustic signal. Seventy-two growing pigs were assigned to groups of three and three different treatments: anticipated enrichment (aE), enrichment-only (Eo), and control (C). In the aE and the Eo groups, the ball was presented 10 times per week at different times of day for 10min each during the fattening period. In the aE treatment, the ball was presented 30s after a pen-specific tone sequence was played. In the Eo treatment, pen-specific tone sequences were played also, but the ball was provided without temporal link to these tone sequences. Pigs in the C treatment could hear the tone sequences and see other pigs interacting with the ball, but neither had a pen-specific tone sequence nor ever received the ball. In general, neither activity nor social behaviour was affected by treatment. Pigs in the aE treatment, however, exhibited increased activity during the anticipatory period. In contrast, pigs in the other treatments exhibited no increased activity after hearing tone sequences. Pigs in aE and Eo treatment spent an average of 5min interacting with the ball (1min) or corn (4min). Trial number did not significantly affect the duration of interacting with the ball or number of agonistic interactions while the ball was present in the pen. We conclude that this short-time enrichment, especially when delivered following a period of anticipation, is steadily attractive for growing pigs. The cognitive aspect of the enrichment used in this study may be an additional possibility to improve animal welfare in combination with conventional enrichment strategies.