Use of infrared thermal technology to detect changes in neonatal lamb temperature

Abstract

The capacity to mount a response to cold stress is an important determinant of the probability of lamb survival (Slee, 1981). The aim of this experiment was to determine if changes in the body temperature of lambs born to ewes fed differentially during the last 50 days of pregnancy could be detected before and after a noradrenalin challenge using infrared thermal (IRT) technology. Ewes were oestrous synchronised, mated and maintained on pasture until day 100 after joining. At day 60 after mating, they were scanned for pregnancy and litter size. From day 100, single- or twin-bearing ewes were fed either an 80% or a 120% maintenance energy diet, resulting in four groups of ewes: single 80% (n=4, 8.4 MJ ME/day), twin 80% (n=5, 10.2 MJ ME/day), single 120% (n=5, 12.6 MJ ME/day) and twin 120% (n=4, 15.6 MJ ME/day). The ewes were penned individually indoors on day 143 of pregnancy. At 5.5 hours of age, temperature loggers were inserted into the rectums of the lambs. At 6 hours of age, lambs were given a noradrenalin injection (150 μg/kg) subcutaneously in the mid dorsal region. A dorsal IRT image of the lamb was taken immediately prior to and 30 min after the injection. A midline temperature profile from the shoulder to rump was extracted from the IRT image and the area under the curve (AUC) was calculated. The maximum temperature before and after the injection and the relative location of the maximum were recorded. Rectal temperature at the time of the injection and 30 min after the injection was determined. Data were analysed using litter size as a main effect and nutritional level (MJ ME/day) as a covariate.