Decrease in body surface temperature before parturition in ewes

This study investigated the correlation between the body surface temperature (BST) and core body temperature of ewes and changes in BST during the prepartum stage in pregnant ewes. Four non-pregnant adult ewes were used in the first experiment. The BST of the upper neck, vaginal temperature (VT), and ambient temperature (AT) were measured every 10 min for seven days and analyzed for correlations. The mean (± SD) BST and VT of ewes during the study period were 35.4 ± 1.7°C and 39.1 ± 0.4°C, respectively, with a correlation of r = 0.62, P < 0.001. This finding suggested that the BST was associated with core body temperature in ewes. In the subsequent experiment, seven pregnant ewes in their third trimester were used to evaluate changes in BST measured at the upper neck 72 h before parturition. The mean BST at -24-0 h (0 h = time of parturition) was significantly lower than that at -72- -48 h and -48- -24 h (P < 0.05). The BST tended to decrease toward parturition; all BST measurements at -16- -3 h were significantly lower than those at -72 h (P < 0.05). A clear circadian rhythm in the BST was observed at two days and the day before parturition and an unclear circadian rhythm was observed on the day of parturition. Therefore, these findings indicate that the BST also decreases before parturition, as do vaginal and rectal temperatures.