Maximizing Genetic Return on a Valuable, Terminally Injured Cow
A 3.5 year old Registered Holstein cow presented to the Cornell University Equine and Farm Animal Hospital after being found recumbent in the field. She was housed with a group of other dry cows and had been witnessed to be normal the night before. The owners reported that she was genetically valuable, had been used for in-vitro fertilization, and was 238 days pregnant. Upon presentation, she was bright, alert, and responsive and continued to eat hay when offered. On physical exam, she was eupneic and normothermic, but tachycardic (96bpm) with a body condition score of 8/9. She was non-ambulatory with apparent normal function of her thoracic limbs, but a full assessment of her pelvic limbs was not possible due to her recumbency. Initial laboratory testing revealed that she was dehydrated and hypocalcemic with both a respiratory and metabolic alkalosis. Due to her status as a dry cow, her good appetite and attitude, and her failure to improve after initial stabilization of the abnormalities identified during her initial diagnostic testing, it was determined that traumatic injury was the most likely cause of her recumbency. Supportive care and pain management were provided until the patient stabilized enough to attempt floatation after about 3 days. At that time, she failed to bear weight on either pelvic limb suggesting a poor prognosis. Ultrasound imaging revealed a dorsally luxated right femoral head. No images of the left femoral head or acetabulum could be obtained. She was ultimately euthanized and necropsy revealed bilateral hip luxation, left gluteal muscle avulsion, diffuse pulmonary edema, and mild heart disease, which was thought to pre-date her injury. After determining her poor prognosis, the focus of care turned to maximizing the genetic potential that could be obtained at the end of her life. Multiple options were considered including maturation of fetal lungs and pre-term terminal caesarian section in an attempt to save the calf, ovarian super-stimulation with ovarian collection prior to euthanasia, collection of tissue for cloning, or combinations of these technologies. Unfortunately, the medication most commonly used to mature fetal lungs, dexamethasone, has been linked to poor oocyte quality during ovarian super-stimulation, so combination of these technologies required careful analysis of the risks versus potential benefits. Additionally, while ovarian follicular waves have been shown to continue through the eighth month of pregnancy, the mean numbers of waves and the numbers of follicles per month sharply declined between months eight and nine. The benefits of dexamethasone to obtain a viable calf must therefore be weighed against its detrimental effects on in-vitro fertilization rates that are already compromised due to her stage of pregnancy. With the advent of affordable genomic testing for cattle, it has become much easier and less expensive for producers to identify the most genetically valuable animals within a herd. The biggest benefit of this technology is allowing the producer to utilize advanced reproductive technologies to obtain multiple offspring from a valuable animal within a short period of time. This article will discuss the benefits, challenges, and potential success rates of pre-term caesarian section versus ovarian super-stimulation and IVF in an attempt to maximize the genetic potential of a terminally injured valuable cow in late gestation.
Cows; Caesarian Section; In-Vitro Fertilization; Cloning; Terminal Injury; Dexamethasone; Pre-Term Calf; Case Studies
dissertation or thesis