Characteristics and analysis of uterine electromyographic activity in pregnant cows

The electromyographic activity of the cow uterus in the last trimester of pregnancy was investigated. The investigation was performed on 12 animals and the electrical activity was recorded in the last trimester of pregnancy during 11 different periods until the delivery. The duration of the action potential bursts (APB) recorded during the first 7 periods, was small. It did not exceed 2 seconds. A significant increase, however, was recorded at 7 to 9 days before the labor and it involved all the investigated areas in the uterus. The number of APB of the gravid horn was significantly higher than that recorded at other locations in the uterus with the exception of the day of delivery. A significant correlation was found between the number of APB and the level of magnesium in blood serum. The levels of 17-beta estradiol and progesterone were similar during all studied periods with the exception of the last week, in which a dramatic fall in estradiol level and a significant increase in the progesterone concentration were observed. The results showed that it is possible to distinguish three different phases of electric activity in the cow uterus during the last trimester of pregnancy. The features of these phases were discussed.