Effect of Ovariectomy on Pregnancy Maintenance and Parturition in Dairy Cows

Abstract

Forty-one cows of three dairy breeds were ovariectomized by laparotomy at 48–268 days of pregnancy to determine the effects on gestation length and parturition. No differences existed between bilateral ovariectomy and removing only the ovary containing the corpus luteum (unilateral), nor did breed differences exist. Twelve cows ovariectomized at 48–117 days of pregnancy aborted an average of four days after removal of the luteal tissue. Ovariectomy of eight cows at 139–174 days resulted in abortion an average of 23 days later. Twenty-one cows ovariectomized at 200–268 days of pregnancy terminated in 2–74 days (X¯=33) at an average gestation length of 262 days. Based on previous history of these cows, the expected gestation length was 278 days. Of the 41 cows, 36 had retained fetal membranes and 26 fetuses or calves died prepartum. Calving difficulties due to partial cervical dilation and uterine inertia, and postpartum metritis were common. The corpus luteum of pregnancy appeared essential for maintaining pregnancy in the bovine prior to Days 165–180; thereafter, a viable fetus was sometimes maintained in the absence of the gland. However, the corpus luteum was essential during late pregnancy to prevent shortened gestations and abnormal parturitions, including retention of the fetal membranes. © 1967, American Dairy Science Association. All rights reserved.