A Review of Assessment of Sow Pain During Farrowing Using Grimace Scores

Reproduction is one of the most important considerations for the livestock industry, presenting significant economic and animal health and welfare pressures for producers. Parturition, the process of giving birth, is known to be highly painful in many mammalian species, but the understanding of parturient pain in sows is limited. Farrowing, the process of parturition in pigs, is understudied compared to other livestock species, with very little research available specifically regarding pain. Pain can be detrimental to animal wellbeing; hence, it is vital for it to be reliably detected and managed in such a way that improves both sow and piglet health and welfare. Grimace scales have been developed as a method for pain detection and quantification in animals via observations of facial expression changes in response to painful stimuli. This presents a unique opportunity for improved pain assessment during farrowing, increasing the current understanding of farrowing dynamics and potentially enhancing farrowing management decisions to prioritise sow welfare. This review synthesises and critically analyses the current knowledge on sow parturient pain and the ability for the application of facial grimace scoring to measure pain severity. Grimace scoring was found to be an effective, simple and feasible method of pain assessment in a number of domestic species, and its recent application to farrowing is a promising development in the understanding and management of sow welfare during parturition.