A review of methods to measure animal body temperature in precision farming

The authors wish to thank colleagues from INRA, Eric Bobillier, Alain Ducos and Pierre-Yves Lebail for their helpful discussion, Michael Bertoldo (INRA) and Sandra Martin (Texas A&M University) for English proofreading.Automation of phenotypic measurements of livestock has become a more important goal for scientists and also for farmers who need a more precise, real-time knowledge of their animals. Among physiological measures, body temperature and its variations are key indicators of the physiological health and well-being of animals. Although measuring the body temperature may seem a trivial matter, its implementation is faced with many difficulties both at biological and technological levels in a field of constant progress. Today, there are many studies reporting taking temperature measurements without restraining animals. The present report focuses on the two main approaches to temperature measurements that use direct contact or radiation sensors. Specifically, we investigated the use of thermocouples, thermistors and infrared radiation sensors. A wide literature review using one of these techniques was conducted in which different animal species, different purposes, different experimental designs, various equipments, and different devices and gold standard methods are discussed. These technologies will continue their dizzying development, leading to new communication protocols, sensors miniaturization and a more efficient management of energy. These developments will have a direct impact on the increase of reading distances and the amount of information stored. In response to the request of farmers and researchers, integrated monitoring systems are already marketed with user-friendly interfaces and softwares for complex data storage and treatments