Neonatal piglet core body temperature model from surface temperature and environment measurements

Piglet core body temperature (CBT) can drop rapidly after birth, and the magnitude of this drop as well as delayed recovery to homoeothermic status can compromise the vigor of piglets. Recent research has demonstrated that mean body temperature reductions of 4.4°C can occur within the first 30 min after birth, with some individuals experiencing reductions of as much as 8°C, with average recovery times to birth temperature of greater than 4h. Measuring piglet CBT at birth is not generally practical in production facilities, but a simple method to estimate CBT from body surface infrared measurements and the farrowing room thermal conditions would be a useful assessment tool. The objective of this research is to develop and evaluate simple models that relate piglet body surface temperature and room conditions to piglet CBT as estimated from rectal temperature. Thermal images, along with corresponding farrowing room temperature and relative humidity, were recorded for a group of 99 neonatal piglets. Rectal temperatures were measured at birth and 15, 30, 45, 60, 90 120, 180, 240 min, and 24 h, after birth. Three models, linear, polynomial, and a non-linear surface model were developed to predict piglets’ CBT from body surface temperatures measured behind the ears of the piglets, air temperature, wet-bulb temperature, wet-bulb temperature depression, and elapsed time post-birth. The linear and non-linear surface fitting models provided better prediction over the polynomial model (adjusted r²=0.7, 0.3 and 0.2, respectively). A refined linear model was developed using only maximum ear surface temperature for dry piglets 45-min or greater after birth, which reasonably predicts rectal temperature (adjusted r²=0.81, RMS error = 1.2°C) and can be used as a convenient prediction tool for rapid estimation of piglet CBT under typical farrowing conditions.