Puerperal period of cows
The puerperal period is the period between birth and complete uterine involution, which is around 40 days postpartum for cows. Progesterone levels decline rapidly during the last 48 hours before parturition and remain at very low levels throughout the early post calving period. This decline is related to regression of the corpus luteum of pregnancy. Shortly after calving, the uterus is very large, which the weight represents between 8 to 10 kg. The most part of uterine involution takes place between calving and day three post calving. Vasoconstriction and peristaltic contractions allow a rapid decrease in size. Uterine involution is also characterized by a necrosis of caruncular stalk, breakdown of the superficial layer of the caruncle and formation of the lochial discharge. This event is completed about 12 days after calving and normally is an aseptic process. However, puerperal infections can occur when massive bacterial growth in the lochia. In this case cows have more predispositions to manifest gynecological troubles as placenta retention and metritis.