Surface temperature of ewes during estrous cycle measured by infrared thermography

Abstract

The use of infrared thermography has not been used previously to assist sheep reproduction. The aim of this study was evaluate the viability of infrared thermography to identify body surface temperature patterns during ewes' estrous cycle. The estrous cycles of 20 Santa Ines ewes were synchronized through hormone treatment (progesterone implant). The ewes were submitted to measurements of body temperature (rectal and vaginal) with a digital thermometer and surface temperature of the anus, vulva, muzzle, left ear and left eye by infrared thermography. Temperature and humidity of the environment and wet-bulb globe temperature (WBGT) were measured. After the progesterone implant's removal, the follicular dynamic was evaluated daily during five days with ultrasound. The estrous cycle was separated into six phases to facilitate interpretation of the differences in body temperatures in each period. Phase 1 was the period before estrous synchronization, phase 2 was the beginning of estrous synchronization, phase 3 was the intermediate period and end of synchronization, phase 4 was the period of estrus manifestations, phase 5 was the ovulation period, and phase 6 was the post-ovulatory period. There was a difference among phases for all body regions evaluated (P < 0.05). All temperatures were higher in the ovulation phase. The rectal and vaginal temperatures measured by digital thermometer were lower during the diestrus period and increased during and after ovulation. The surface temperature of the vulva, measured by thermography, was higher from the estrus phase (4) to the ovulation and post-ovulation phases (5 and 6). The surface temperature of the muzzle was higher from the ovulation phase (5) to the post-ovulation phase (6), showing potential to detect ovulation. The thermography was efficient to detect small temperature variations during different phases of the estrous cycle, allowing the identification of different phases of the cycle in Santa Ines ewes.