Location: Warmwater Aquaculture Research UnitTitle: The use of digital infrared thermal imaging to detect estrus in gilts Author
Submitted to: Theriogenology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2012
Publication Date: 7/1/2012
Citation: Sykes, D.J., Couvillion, J.S., Cromiak, A., Bowers, S., Schenck, E., Crenshaw, M., Ryan, P. 2012. The use of digital infrared thermal imaging to detect estrus in gilts. Theriogenology. 78:147-152. Interpretive Summary: Digital infrared thermal imaging (DITI) is a noninvasive technique which can be used to detect symmetric and asymmetric temperature gradients of surface areas. The purpose of this study was to investigate the use of DITI to differentiate between temperature gradients of the vulva during different stages of the reproductive cycle in the pig. Based on the current data, DITI can discriminate between vulva surface temperatures during estrus and diestrus in gilts. This information could be used to determine at what time points of the estrous cycle surface temperature of the vulva begins to increase, reaches its peak surface temperature, and returns to baseline. The ability to detect these changes in vulva thermal signatures could provide a means for early detection of the onset of estrus. Thermal imaging could also provide a method of identifying estrus noninvasively in appropriate zoological species.
Technical Abstract: Yorkshire/Landrace crossbred gilts (N =32) were evaluated using digital infrared thermal imaging (DITI) to discriminate between estrus and diestrus phases of the porcine estrous cycle. Gilts (N =32) were part of an ongoing reproductive efficiency study involving the use of raw soybean (RSB; N = 15) versus soybean meal (SBM; N = 17) as a source of dietary protein. Gilts were monitored daily for signs of estrus using a teaser boar. Thermal images of vulva surface temperatures (TEMP) were recorded at standing estrus and diestrus. Measurements for analysis included minimum (MIN), maximum (MAX), mean (AVG), and standard deviation (SD) of temperature gradients. At imaging, ambient (AMB) and rectal temperatures (RT) were recorded, and blood samples taken for serum progesterone (P4) concentration analysis (by RIA) to confirm stage of cycle. Mean serum progesterone values at estrus and diestrus were (mean ± SD) 1.0 ± 0.1 and 10.9 ± 0.8 ng/mL, respectively. Vulva MIN, MAX, and AVG thermal images were positively correlated with one another (P < 0.01), and were positively correlated with ambient temperature (P < 0.01). Vulva MAX and AVG thermal temperatures were greater (P < 0.05) at estrus than at diestrus (36.6 ±0.2 °C and 33.4 ± 0.3 °C vs. 35.6 ± 0.3 °C and 31.8 ± 0.6 °C, respectively), whereas MIN and SD had no differences (P < 0.05) between stages of the cycle. No differences (P < 0.05) in RT were detected between stages and RT was not significantly correlated with vulva thermal images. Diet had no significant effect on RT or vulva temperature.