Behavior of pigs in enriched environment: alternatives to extend the animals’ interest towards the enrichment

The objective of this research was to evaluate the effects of the frequency of provision of environmental enrichment objects on the duration of animals' interest towards the enrichment. The animals (n=184), males and females pigs, in growth phase, were distributed in completely randomized design in four treatments: 1) control without enrichment objects; 2) objects offered for six consecutive days without interruption; 3) objects offered in alternate days; 4) objects offered for six consecutive days removed in the late afternoon and put back in the morning. The environmental enrichment objects were made of PVC tube measuring 25 cm in length coupled with four plastic hose pieces measuring 65 cm each, which allowed the pigs develop exploratory activity and chewing. Six consecutive days of behavioral observations were done, from 7:30 to 15:30hs, in 10-minutes intervals, using images obtained with the assistance of video cameras. The observations were used for the construction of a frequency histogram based on the behaviors listed in an ethogram (interacting with the object, agonistic behavior, rooting and exploring the environment, eating and drinking, lying and sleeping, sexual behavior, seated, nosing or rooting a pen mate, playing). The behavior was analyzed individually, and each animal was considered an experimental unit. Analyses of variance were performed and means were compared by Tukey test (p<0.05). The different methods of providing environmental enrichment objects not influenced the time that animals spent interacting with the object (p>0.05) (9.69, 9.05 and 11.98% of the total estimated time, for T2, T3 and T4, respectively). The time spent with agonistic and exploratory behaviors was similar in all treatments (p>0.05). It was expected that the fact that the objects are offered on alternate days or be removed in the evening and put back in the morning, could stimulate greater interest of the animals for them and become an effective strategy to prolong the positive effects of enrichment. However, this was not observed and the time spent by the animals interacting with the objects was similar for the three enriched treatments, as well as the frequency of interaction throughout the trial period. The form of supply of environmental enrichment factors did not influence the success of their use. We conclude that the provision of enrichment on alternate days or its removal at the end of the day may not be efficient strategies to increase the interest of the animals towards the enrichment items.