Short communication: behavioral and physiological indicators of sensitivity or chronic pain following tail docking.

Docking the tails of dairy cattle causes mild to moderate behavior changes and physiological indicators of acute pain, but no studies have investigated the possibility that tail docking may lead to chronic pain. In human amputees, an incidence of increased limb surface temperature is associated with phantom limb pain, a central nervous system representation that survives peripheral loss. The objectives of this study were to assess indicators of sensitivity or chronic pain in heifers by using behavioral indicators and thermography. We tested 14 Holstein heifers, 7 docked and 7 intact, from a previous neonatal tail-docking experiment. All 14 animals were videotaped during a test sequence of alternating cold (-9 degrees C), hot (54 degrees C), and neutral packs applied to the underside of the tail. Packs were placed approximately 30.5 cm from the tail head on all animals. A thermal image of the tail was taken using infrared imagery prior to and after temperature sensitivity testing. Docked heifers tended to have greater changes in surface temperatures following the test sequence than did nondocked heifers. In docked heifers, temperatures on the underside of the tail were higher than those at the tip of the tail, both prior to and following the test sequence. Docked heifers also showed substantially higher stomping activity following application of the cold pack. Shifting increased in intact heifers after application of the hot pack, but shifting of the docked heifers did not change. Greater changes were observed in the tail surface temperatures of the docked heifers following temperature manipulation, similar to human amputees who are experiencing phantom limb pain, indicating that similar mechanisms are present in the stump of the docked tail. The behaviors of docked heifers indicated changes in their sensitivity to heat and cold.