What a pig sees when it looks into a mirror may help researchers with the U.S. Department of Agriculture's Agricultural Research Service (ARS) improve livestock housing.

Animal scientist Jeremy Marchant-Forde and his colleagues at the ARS Livestock Behavior Research Unit in West Lafayette, Ind., study livestock behavior, stress and other well-being and production factors. Improving an animal's environment can reduce stress, which, in turn, may enhance well-being, growth and efficiency and decreases disease susceptibility.

In a study, Marchant-Forde looked at different types of pig pens. Pigs had access to either a standard pen with a metal floor (the control pen), one with a rubber mat on the floor, another with a mirror or a fourth with a view of another pig across a passageway.

Pigs preferred spending 40% of their time in pens where they could see another pig. They spent 10%, 20% and 30%, respectively, in the control, mirror and mat pens.

In a second experiment, scientists examined which pens pigs preferred when a person was present. When a person was in sight, pigs spent nearly 90% of their time in either the pen with the mirror or where they could see another pig. Marchant-Forde hypothesized that pigs saw their reflection in the mirror as a companion; however, more research is needed for confirmation, ARS said.

Having mirrors in a commercial production, where pigs are kept in groups, would not be feasible, Marchant-Forde noted. However, producers could consider using rubber mats to help improve the pigs' environment, which may help reduce stress and promote health and productivity.