Forty-eight domestic pigs were used proliferative response than socially dominant or suborto
evaluate the effects of heat and social stress on dinate pigs. Many immune measures showed a
immune indices. Pigs were brought together in groups significant interaction between heat and social stress
of three per pen and video-taped for the first 72 h. over days of the study. Generally, socially dominant or
Video tapes were viewed to determine time spent in submissive pigs had alterations in immune function
aggressive and submissive behaviors. Social status of (elevated numbers of neutrophils, decreased antibody
each pig was determined from outcomes of agonistic production) compared with socially intermediate pigs.
interactions. Pens of pigs were housed in either a In conclusion, heat and social stress interact in their
thermoneural (control, 24°C) or heat-stress (33°C) effect on the pig's immune system. Although one
air temperature. Immune measures were determined might have predicted immunosuppression among subfrom
blood samples obtained on d 0, 7, 14, 21, and 28 missive pigs, there also seemed to be immunological
after grouping. Social status had an effect ( P < .05) on costs to dominant pigs as well. These data also have
lymphocyte proliferation in response to pokeweed implications in design of stressor research in that
mitogen: socially intermediate pigs had a higher social behavior should be measured or controlled.
Key Words: Stress, Pigs, Social Environment, Heat Stress, Immunity