Increase in milk and body temperature of cows as a sign of embryo entry into the uterus

The objective of the first stage of these studies was to investigate whethe r temperature increases in the milk and body of cows during the early perio d of pregnancy. We studied 94 pregnant and 116 nonpregnant cows, and the te mperatures were measured daily beginning 24 days after insemination. In add ition, progesterone levels in milk were measured twice (on Days 21 and 24 a fter insemination), and examinations per rectum were conducted to determine pregnancy. Data analysis showed that in almost 90% of the pregnant cows mi lk temperature increased by 0.64 degreesC some time between Days 5 and 12 a fter insemination. This increase in milk temperature was highly significant and corresponded with a 0.46 degreesC increase in body temperature. There was no increase in the milk or body temperature in nonpregnant cows. After discovering in the first stage that a high percentage of pregnant cows expe rienced both milk and body temperature increases, we focused our attention in the second stage of the study on the question of whether this increase i n temperatures might be due to an immune response of the mother to the entr y of the embryo into the uterus. In this stage we conducted three different experiments on another group of animals consisting of 309 cows and heifers . The experiments included analysis of progesterone, estradiol, cortisol an d PGE(2) levels in the blood serum of the cows and heifers; an estimation o f the pyrogenic activity of PGE(1), PGE(2) and progesterone; and measuremen ts of body temperature in the heifers before and after embryo transfer. The results of these experiments suggested that an increase in milk and body t emperature could be an indicator of an immune response of the mother to the entry of the embryo into the uterus. (C) 2001 by Elsevier Science Inc.