Relationship Between Ovulation and Body Temperature in the Mare: A Preliminary Study

In the equine industry, monitoring of the reproduction cycle is key to be able to produce one foal per mare and per year. Ovulation detection is difficult partly due to the variability of the estrus length. Currently, the most reliable method for ovulation detection is transrectal ultrasonography. This technique, however, implies handling of the mare as well as veterinary costs. The aim of this experimentation is to study body temperature variations around ovulation. Nine reproduction cycles were monitored around ovulation. Transrectal ultrasonographies were performed each day as well as blood sampling to dose estradiol-17 beta and progesterone to confirm ultrasonographic results. Body temperature was automatically recorded every 10 minutes using an identification chip equipped with a temperature sensor implanted in the mares' neckline. Data were analyzed using linear mixed models. Daily body temperature pattern did not vary between the phases of the reproductive cycle (follicular, ovulatory and luteal). Temperature dif-ferences between phases, however, were identified and appeared hourly-specific. There was an increase of temperature at ovulation compared to the end of the follicular phase ranging from 0.51 C-degrees +/- 0.21 C-degrees to 0.92 C-degrees +/- 0.26 C-degrees and occurring between 04:30 and 08:00. Moreover, a significant increase of body tem-perature was measured during the first days of luteal phase, ranging from 0.29 C-degrees +/- 0.17 C-degrees to 0.60 C-degrees +/- 0.16 C-degrees, between 10:30 and 16:00. Body temperature varied around ovulation and it might be a promising tool for mare reproduction monitoring. A more complete study, however, focusing on the whole cycle is required.(c) 2023 Elsevier Inc. All rights reserved.

Automated summary

The aim of this study was to investigate body temperature variations around ovulation in horses. The results showed an increase in temperature at ovulation and a significant increase during the first days of the luteal phase. These findings suggest that body temperature fluctuations could be a promising tool for monitoring mare reproduction.