Pain and discomfort caused by parturition in cows and sows

This review focuses on parturition as a painful process in cows and sows. Firstly, the different stages of parturition associated to the origin and transmission of pain stimuli are described. Hypoalgesia during the late pregnancy and parturition has been shown, perhaps as an endogenous defence against the pain of parturition. The principal factors affecting parturition pain are parity and dystocia, which are more likely in cases of long parturition, feto-pelvic disproportion and/or foetal malpresentation. The main consequences of pain caused by parturition are reviewed; parturition is an intrinsically risky process for both mother and young and can cause a stress response, health problems and maternal mortality, in addition to decreased food intake and production. The assessment of parturition pain has tended to use one of three approaches: measures of general indices, physiological and behavioural indicators. Finally, the impact of analgesia after parturition in cows and sows is reviewed. It is concluded that pain caused by parturition in animals deserves more research in order to optimize the parturition process and reduce its negative consequences on health, welfare and productivity. (C) 2011 Elsevier B.V. All rights reserved.