Presence of a Temperature Gradient Among Genital Tract Portions and the Thermal Changes Within These Portions Over the Estrous Cycle in Beef Cows

The aim of the present study was to describe the temperature of the different portionsof the female genital tract and their relation to rectal temperature and to investigatethe effect of steroid hormones profiles on these variables over the estrous cycle incattle. Four nonpregnant Japanese Black cows were investigated daily over two successiveestrous cycles using a digital thermometer with a long probe and rounded-end sensor torecord the temperature of the rectum (RT), vagina (VT), cervix (CT), uterine body (UBT)and uterine horns (UHT). Blood samples were collected immediately before temperaturerecording to assay peripheral levels of progesterone (P₄) and estradiol-17β(E₂). Moreover, transrectal ultrasonography was carried out after temperaturerecording to monitor the ovulatory follicle and track ovulation. During the experiment,the ambient temperature and relative humidity were recorded for further calculation of thetemperature humidity index (THI). The temperature within the genital tracts in these cowsprogressively increased towards the uterine horns from the vagina. The VT, CT, UBT andUHTs were significantly higher in association with peripheral P₄ concentrationsgreater than 4 ng/ml (mid-luteal phase) when compared with lower peripheral P₄concentrations. The VT was more significantly (P<0.01) correlated to the CT, UBT andUHTs than RT. In conclusion, a temperature gradient was present among the vagina, cervixand uterus over the estrous cycle, and changes in peripheral P₄ concentrationswere associated with the thermal variations within these portions. The VT could be morebeneficial than RT in monitoring temperature of deeper portions of the female genitaltract in bovine.