Objective: To determine if changes in vulvar skin temperature (VST), measured using infrared thermography (IRT), occur during estrus.

Materials and methods: The experimental groups consisted of 25 gilts and 27 multiparous sows. Infrared VST and gluteal skin temperature (GST) were measured twice daily (8:00 am and 4:00 pm) using a thermal-imaging camera (Fluke IR FlexCam; Fluke Corporation, Everett, Washington). Once standing estrus was observed, transrectal real-time B-mode ultrasonography was performed twice daily (8:00 am and 4:00 pm) to monitor follicle development and determine time of ovulation. Mean VST and GST (± SEM) were reported and compared using MANOVA and Tukey-Kramer tests in SAS 9.1 (SAS Inc, Cary, North Carolina). Significant differences were reported at P <.05.

Results: Evidence of ovulation was detected at approximately 38 ± 9 and 43 ± 12 hours after the onset of estrus in gilts and sows, respectively. Overall, daily VST and GST were significantly higher (P < .05) in sows than in gilts. During estrus, VST rose as estrus began and fell significantly (1.5°C; P < .05) 36 to 12 hours prior to ovulation in both sows and gilts. There was no significant difference between daily GST measurements (P > .05), but the difference between VST and GST was significant (P < .01) over time.

Implications: This study demonstrated that VST of sows and gilts, measured by IRT, changes significantly during estrus. The potential to use digital infrared thermography as an adjunct tool during estrus detection in swine appears to be promising.