In postpartum dairy cows, rapid uterine involution is a prerequisite for a high conception rate and short interval from calving to conception (Opsomer et al., 2000). The uterus shows a distinct
size reduction during the first 3 weeks postpartum (pp), with uterine contractility crucial in the process of uterine involution, particularly with regard to the removal of excessive fluid and debris and the elimination of bacteria from the uterine lumen during the early postpartum period (Zerobin and Sporri, 1972; Paisley et al., 1986; Arthur et al., 1996).