There is a marked decline in body temperature in animals immediately before parturition.
Beginning at least one week before lambing, Australian researchers recorded the rectal temperatures of 106 single and twin-bearing Corriedale ewes with 9 months of fleece growth.
A fall in rectal temperature below 39.20°C (102.6°F) or 39.85°C (103.7°F) occurred respectively in more than 80% of single and twin-bearing ewes within 48 hours of lambing. Similar falls in rectal temperature were also recorded in about 20% of ewes more than 48 hours from lambing.
Source: Livestock Production Science , Volume 2 , Issue 4.