Relationship between Environmental Enrichment and the Response to Novelty in Laboratory-housed Pigs

Abstract

Environmental enrichment is the enhancement of the physical or social environment in which an animal lives with the goal to improve its quality of life. Our objective was to investigate the effect of providing environmental enrichment in the home pen on responsiveness to novelty in laboratory-housed pigs. Pigs were housed (4 pigs per pen) in enriched (n = 32) or barren (control; n = 32) pens for 3 wk total and tested in 2 anxiety behavioral tests, the novel object (NOT) and human interaction (HIT) tests. Pigs were placed in a novel arena for a 5-min familiarization period, after which either a novel object (NOT) or an unfamiliar human (HIT) was introduced for a 5-min interaction period. Behavior in the home pen and during NOT and HIT was monitored through direct observations and videorecording. In the home pen, enriched pigs spent more time active and interacting with the environment, whereas control pigs spent more time inactive and in social interactions. In addition, enriched pigs crossed more squares during the familiarization period, tended to freeze more, and interacted less with the novel object or person than control pigs. In conclusion, enrichment may improve welfare by stimulating activity and decreasing aggressive behaviors in the home pen. However, enriched pigs may experience increased anxiety when exposed to novelty, whereas pigs housed without environmental enrichment-due to lack of stimulation in the home pen-may be more motivated to interact with sources of novelty or enrichment during testing than their enriched counterparts.

Figure 1.

Environmentally enriched pigs (A) interacting with toys and substrates, (B) getting treats, and (C) interacting with a person in the home pen.

Figure 2.

Descriptions of behaviors monitored in the home pen and during the behavioral tests.

Figure 3.

Arena layout for the novel object and human interaction tests. The arc indicates the entrance–exit, and the filled circle indicates the location of the novel object or unfamiliar person.

Figure 4.

The percentage of total observations (least-squares mean ± SEM) that pigs spent performing different behaviors over a 48-h observation period in standard (control, CON) or environmentally enriched (EE) pen. *, Values differ significantly (P < 0.05) between groups.

Figure 5.

Number of squares crossed (least-squares mean ± SEM) by pigs during the familiarization and interaction period of the novel object and human interaction tests. Pigs were either housed in enriched (n = 32; EE) or barren, control (n = 32; CON) pens prior to testing. Different superscripted lowercase letters indicate values that differ (P ≤ 0.051).