Placental relationships to parturition in dairy cattle

Two trials were conducted to observe placental relationships to parturition in dairy cattle. The objective of the first study was to determine factors affecting the volume of blood retained in the placenta following delivery of the calf. In addition, a technique was developed for accurately measuring the volume of blood retained in the placenta following delivery. Blood remaining within the placenta was calculated using an algorithm that included cotyledonary weight, cotyledonary [Hb], and calf blood [Hb]. Factors that were associated with residual placental blood volume included cotyledon hemoglobin concentration, placental weight, and calf hemoglobin concentration. The only factor that significantly affected placental expulsion time was the weight of the placenta. In the second trial calves (n=70) and placentae (n=44) were obtained from Holstein cattle following parturition. Delivery parameters include calving ease scores (CES), duration of parturition, calf weight and parity. Placental characteristics evaluated after expulsion included color index (1-light to 5-dark) of cotyledons located at center and tips of placenta, cotyledon number, placental weight and length of umbilical stump. After delivery, calves were weighed, blood samples were collected to evaluate hematocrit, and both length and diameter of umbilical cords were measured. Multiple regression analysis was used to identify explanatory variables associated with each response variable. The only factor that significantly affected placental expulsion time was umbilical cord break point. Factors that affected duration of calving included parity, diameter of umbilical stump, calf weight, total length of umbilical cord and calf umbilical cord efficiency (calf weight/diameter of umbilical stump). Factors affecting CES included color index in center of placenta, color index in tips of placenta, diameter of the umbilical stump, cotyledon number, and umbilical cord break point. Finally, the only factor that affected calf weight was weight of the placenta. The data strongly reflects the relationship between placental factors, delivery parameters and calf outcomes