Increase of Body Temperature Immediately After Ovulation in Mares.

To successfully inseminate mares, precise detection of ovulation time is crucial, especially when using frozen-thawed semen. Monitoring body temperature, as has been described in women, could be a noninvasive way to detect ovulation. The objective of this study was to investigate the relationship between the time of ovulation and the variation of body temperature in mares based on automatic continuous measurements during estrus. The experimental group included 21 mares for 70 analyzed estrous cycles. When the mares showed estrous behavior, they were administered intramuscular deslorelin acetate (2.25 mg) in the evening. At the same time, monitoring of body temperature using a sensor device fixed at the left lateral thorax was started and continued for over 60 hours. In 2-hour intervals, transrectal ultrasonography was performed to detect ovulation. Estimated body temperature in the 6 hours following ovulation detection was on average 0.06°C +/- 0.05°C (mean +/- SD) significantly higher when compared with body temperature at the same time on the preceding day (P = .01). In addition, a significant effect of PGF2α administration for estrus induction on the body temperature was found, being significantly higher until 6 hours before ovulation compared to that of uninduced cycles (P = .005). In conclusion, changes in body temperature during estrus in mares were related to ovulation. The increase in body temperature immediately after ovulation might be used in the future to establish automatized and noninvasive systems to detect ovulation. However, the identified temperature rise is relatively small on average and hardly identifiable in the individual mares.

Increase of skin temperature prior to parturition in mares.

Prediction of impending foaling is highly desirable as early intervention may improve mare and foal outcomes. However, monitoring the peripartum mare is a time-consuming challenge for breeders and many foaling prediction systems have limitations. "Heating up" of the mare is empirically used by breeders as a sign of upcoming parturition in mares. The purpose of this study was to investigate if an increase in skin temperature shortly before parturition is detectable and to determine whether such physiological changes could be an additional valuable parameter to predict foaling. For that, 56 foalings of 14 Warmblood mares, 5 Arabian mares, 27 Thoroughbred mares, and 2 mares of other breeds were analyzed in this 2-year-study. Eight mares were monitored in both years. Mares were between 4 and 22 years old (average: 10 ± 5.5 years) and the mean pregnancy length was 342 days (±9 days), resulting in 14 births from primiparous mares and 42 multiparous mares. For monitoring the periparturient mares, the Piavet® system (Piavita AG, Zurich, Switzerland) was fixed daily when the mares had returned from the field between 4:00 and 6:00 p.m. and collected the next morning between 6:30 and 7:30 a.m. until the time of foaling. Nocturnal rhythms of the skin temperature with the highest values at the start of measurements and a nadir at 6:00 a.m. were observed. On the foaling night, we found a rise in skin temperature starting on average around 90 min prepartum. Skin temperatures recorded at 50 min before parturition and at each 5 min time point until rupture of the allantochorion were significantly higher (p < 0.05) than the mean temperatures measured in the 5 nights before parturition at the same time, reaching a difference of approximately 0.5 °C. There was a significant effect of parity (p = 0.04) on skin temperature during the last hours before foaling where primiparous mares showed a higher mean temperature than uni- or pluriparous mares as early as from 180 min on before parturition. In conclusion, our study shows an increase in skin temperature in most mares within 90 min before birth. Using new biomechanical and digital technologies, this finding could generate an additional potential parameter for the detection of impending parturition. However, skin temperature cannot be used as the only predictive diagnostic of impending parturition in the absence of other parameters.