Preference for and maintenance of interest in suspended enrichment toys in confined growing pigs

The objective of the present study was to evaluate the preference for, interest in, and behavior of growing pigs provided with three different suspended enrichment toys in a four-compartment environmental preference chamber (EPC). Sixty pigs at 70 +/- 2 days of age were divided into two contemporary groups. There were two distinct areas in each compartment of the EPC: one isolated area where two control pigs were housed with access to one type of toy, and one area with free access to the other compartments where five test pigs were housed for 5 days (D-1, D0, D1, D2, D3). Each week, a new group of pigs was introduced into the EPC; this procedure was repeated four times with a different contemporary group. Three different suspended toys (PET bottle; sisal rope; chain) were offered from D1 to D3 and were removed and washed at the end of the day. The toys and a control were randomly arranged in each EPC compartment (control; test). Focal animal sampling with recording interval of 10 min was used to determine the occurrence of behaviors (agonistic, idle, eating, drinking, vocalizing, stereotypic, positive, use of toy, others) from 8:00 to 11:00 h and from 13:00 to 16:00 h. Only for test pigs, for the 'use of toy', we also recorded which toy was being used as well as the duration it was used for. Samples for the determination of salivary cortisol and respiratory rate were taken on alternate days (D0; D2) at 7:0 0 and 13:0 0 h. Data were analyzed by ANOVA with fixed effects of group (test, control), day (D1, D2, D3), and period (7:0 0, 13:0 0 h -cortisol), as well as their interaction. Means were compared by the Tukey-Kramer or t-test ( P < 0.05). The sisal rope was the preferred toy in the test group ( P < 0.05), with a total duration of 70.8 +/- 3.9 min and 36.5 +/- 3.7 bouts, followed by the PET bottle (14.7 +/- 2.2 min; 12.0 +/- 1.6 bouts) and the chain (15.8 +/- 1.4 min; 12.4 +/- 0.9 bouts) ( P > 0.05). Test pigs also exhibited fewer idle bouts compared to control pigs ( P < 0.05). Control pigs preferred the sisal rope ( P < 0.05). Cortisol concentrations did not differ significantly between treatment groups or sampling days, although they numerically decreased by 34.6% (7:00 h) and 17.8% (13:00 h) from D0 to D2. In conclusion, the preferred toy was the sisal rope, with a slight reduction in the number of bouts and duration over three days; however, this toy was still attractive to the pigs and reduced idle behavior when they have the possibility of choosing toys. (C) 2021 Elsevier Inc. All rights reserved.