Examining Environmental Enrichment and Response to Stress
by Brittany Backus, PhD; Animal Care Services, Texas Tech University
A new, enhanced environment can give animals an opportunity to explore and interact. However, when animals are presented with these novel environments, they can be conflicted, with fear of the novelty opposing an instinctual desire to explore. Through a generous Refinement Grant from AWI, we were able to study some effects of enrichment on pigs. Our objective was to determine if rearing pigs with environmental enrichment (EE) would help them to more readily adapt to and cope with the stress of novelty, thereby improving their well-being.
To do this, we housed pigs (4 pigs/pen) for a minimum of two weeks in enriched (EE; n = 32) or standard/control (CON; n = 32) pens. Control pigs had no access to enrichment, but had daily interaction with the husbandry staff. EE pigs had continual access to some enrichment items (ball, PorciChew, hanging water hose), while other enrichment changed daily (shredded paper, peat moss, potting soil, feed sacks, rubber boots, towels, rope, Prima treats, marshmallows, cookies in a rubber Kong toy or football). To habituate them to human interaction, the same lab member spent 15 minutes per day sitting in the pen with the EE pigs, scratching, playing, and feeding them treats. This person was not one of the husbandry staff.
Pigs were then randomly tested in two mild-anxiety behavioral tests. They were placed in a novel arena for a 5-minute familiarization period, after which a novel object (bucket) (Open Field Test) or an unfamiliar person (Human Interaction Test) was introduced for a 5-minute interaction period. The person in the Human Interaction Test took the same pathway entering and exiting the arena. She squatted with head and eyes cast down in a nonthreatening pose. Exploration, the time to interact, and the number and duration of interactions with the novel object or person were determined through live observations and video recording.
Upon entering the arena, EE pigs spent more time exploring the space than CON pigs, so were better able to cope with a novel environment. In both groups, as soon as the novel object or person entered the arena, the pigs spent less time moving around, instead interacting more with the object or person. Interestingly, CON pigs interacted more times with the novel object than EE pigs, suggesting pigs reared in a barren environment may be more motivated to interact with sources of novelty/enrichment. This is opposite of our hypothesis, but the object used may not have been stimulating enough for EE pigs as they had more interactive enrichment in their home pens. All pigs interacted more with the novel object than the person. The pigs may have already become habituated to people, due to normal interactions during daily husbandry, or may still have perceived people as a threat, explaining the shorter time spent interacting with the person as opposed to the object. We also noted that pigs would become frustrated when the human would not interact back.
In conclusion, the results of this study suggest that enrichment creates a positive affective state, enabling pigs to better adapt to and cope with stressors such as a novel environment; however, when assessing the response of pigs to novelty, the level of complexity of the animals’ home pen needs to be considered. In future directions, it would be of interest to see how the type of interaction with the pig (positive, neutral, or negative) in the Human Interaction Test influenced the response to an unfamiliar human.