AUTHOR=Byrd Christopher J. , Young Jennifer M. TITLE=Evaluating the effect of a mild cycling heating period on leukocyte coping capacity in growing pigs JOURNAL=Frontiers in Animal Science VOLUME=4 YEAR=2023 URL=https://www.frontiersin.org/journals/animal-science/articles/10.3389/fanim.2023.1148218 DOI=10.3389/fanim.2023.1148218 ISSN=2673-6225 ABSTRACT=

This study evaluated whether leukocyte coping capacity (LCC) could be an effective method for detecting physiological stress in growing pigs who are exposed to a mild cycling heating period. We hypothesized that whole blood samples collected from pigs exposed to high environmental temperatures would exhibit a reduced respiratory burst response [measured in relative light units (RLU) using chemiluminescence, where reduced RLU levels indicate a smaller respiratory burst size] compared to pigs that were only exposed to thermoneutral temperatures. A secondary objective was to determine the time required for LCC whole blood samples to reach their maximal RLU value following in vitro challenge using phorbol-12-myristate 13-acetate (PMA) to induce a respiratory burst. Forty growing pigs (mean 66.7 kg; range: 54.9 – 87.5 kg) were assigned to 1 of 2 treatments: 1) heat stress (HS; n = 20), or 2) thermoneutral (TN; n = 20). The HS pigs experienced a cycling mild heat stress period over 48 h (range: 19.5-28.6°C), while TN pigs were exposed to thermoneutral temperatures (range: 18.9-23.7°C). Whole-blood samples were collected via jugular venipuncture at 0, + 4, +8, +24, and +48 h relative to the start of the cycling heating period and were artificially challenged using PMA. Samples were measured at 0, + 15, and +30 min relative to in vitro challenge. No differences were observed between HS and TN treatments (P = 0.67) and no treatment by hour interaction was detected (P = 0.48). Maximal RLU values were obtained at 15 min post-PMA challenge (P < 0.05).