317
A technique to ovariohysterectomize cattle for use in gestational research
The time period from conception through the embryonic stage of development is critical in terms of establishment, recognition, and maintenance of pregnancy to term. Research on factors influencing embryonic development up to d 14 is relatively simple. Much less is known about the influences on conceptus (embryo and membranes) development from the time embryo flushing becomes impossible to the end of the embryonic stage (~d 16 to d 50 in bovine). To access this critical period we developed and optimized a standing flank hysterectomy procedure. Protocols for ovariectomy and cesarean section from veterinary medicine and research practices were combined and modified, resulting in the technique described herein. Briefly, heifers were placed in a cattle restraining chute and immobilized, administered local anesthetic into the left paralumbar fossa, and given an epidural nerve block. A vertical 18 to 25 cm incision was then made through the skin, muscle layers, and peritoneum into the peritoneal cavity via either blunt dissection or incision. Centauri knots were placed on the right and left uterine arteries, the right and left ovarian spiral arteries, and around the body of the uterus just cranial to the cervix and on the cranial end of cervix. Uterine/ovarian tissue was separated from the broad ligament and incised cranially from ligatures to include as much uterine body as possible. To optimize the procedure Angus crossbred heifers (n = 46; ~ 15 mo of age; BW = 362.3 ± 34.7 kg) were synchronized, bred via AI, and hysterectomized on d 16, 22, 28, 34, 40, or 50 of gestation or not bred (NP) and hysterectomized on d 16 of the estrous cycle. There was a strong negative correlation (r = -0.53, P = 0.0009) between time required for surgical procedure and progression of surgical optimization. Surgery time was least (P = 0.04) in NP controls (69.0 ± 20.8 min). Surgery times were also influenced by stage of gestation (P = 0.04). In pregnant animals, time decreased from d 22 (120.0 ± 12.0 min) to d 40 (79.5 ± 12.0 min); then increased at d 50 (90.5 ± 14.7 min). All heifers fully recovered, were placed on feed, and performed well in the feedlot (1.99 kg/d ADG; 13.77 DMI; 0.145 G:F; 2% Select, 71% Choice, and 27% Prime). This technique offers a plethora of opportunities to explore factors related to pregnancy success and document embryo and placental development in detail.
Keywords:
Bovine, Early Gestation, Ovariohysterectomy