Minimally invasive monitoring methods of pig reproductive state: Oestrus, pregnancy and farrowing - A review.

The pork industry largely operates intensive practices which enables precise herd management through innovative monitoring procedures. However, these must first be evaluated to ensure they are effective and appropriate before implementation. In particular, reproductive status determination has ample scope for improvements as, despite the aid of a few technological advancements, it remains predominantly reliant upon observations, as it has been since the 1950's. Three areas of pig reproduction were identified to have the largest potential for improvement: oestrus detection, pregnancy diagnosis, and parturition onset. Specifically, current oestrus detection methods rely on a set of behavioural cues that culminate in a standing reflex indicative of sexual receptivity and used by stockpersons to implement an insemination protocol. Similar behaviours, alongside real-time ultrasonography, are utilised for pregnancy detection, and parturition onset is estimated based on behavioural and physical signs of oncoming labour. Benefits of advanced monitoring include higher conception rates, reduced reproductive disorders, and increased piglet survival. The aim of this review was to summarise current monitoring methods of these reproductive states and evaluate minimally invasive novel tools within the literature. The majority of identified tools can be categorised as biomarkers or remote technology, for which limitations and barriers to industry uptake have been discussed. Despite advances in machine learning and rapid diagnostics, gaps remain in development of accurate monitoring tools that can be applied to various pig genotypes across their reproductive lifecycle. It is likely that a combination of approaches is key to commercial adoption.