Preservation of Genetics from Dead or Dying Stallions

CHAPTER 44Preservation of Genetics from Dead or Dying Stallions



JAMES K. GRAHAM, CLAIRE. CARD



PRESENTATION OF CLINICAL CASES


The most practical method of genetic preservation of valuable stallions is the cryopreservation of sperm cells. Veterinary practitioners are frequently contacted in emergency situations regarding the preservation of material from valuable stallions that are diagnosed with medical conditions carrying a grave prognosis, suffer lifethreatening illness or injury, or are found dead. Medical conditions that may carry a grave prognosis include advanced renal failure, peritonitis, salmonellosis, pleuropneumonia, disseminated neoplasia (lymphosarcoma, seminoma, melanosarcoma, adenocarcinoma), primary or secondary heart failure, progressive neurologic disease, encephalitis, hepatic encephalopathy, and severe founder. Surgical conditions such as colic related to gastrointestinal torsion, volvulus, and strangulation may carry a poor prognosis for survival. The surgical prognosis depends on a number of factors such as the nature of the gastrointestinal problem, time to referral, and condition of the bowel at surgery. Fatal injuries to stallions may include the following conditions: irreparable cranial, pelvic, limb, or vertebral fractures; chest trauma; diaphragmatic hernias; lacerations causing fatal hemorrhage; and rupture of the suspensory apparatus. Death may be imminent in some cases, or euthanasia may be the only acceptable option. Unfortunately, there is incomplete data on the effect of chemical euthanasia on the viability of samples taken for genetic preservation. Trailer accidents, entrapment, lightning strike, smoke inhalation, predation, poisoning, anaphylactic reactions, electrocution, and drowning account for a small proportion of death losses. Colic in older stallions accounts for the largest percentage of deaths.



DIAGNOSTICS


A physical examination of a disabled or dying stallion is required to determine the prognosis and time frame available for preservation of genetic material. A complete evaluation may include clinical pathologic evaluations of blood, serum, urine, joint fluid, cerebral spinal fluid, and abdominal fluid. Fecal examinations, culture and sensitivity of specimens, radiographs, ultrasonographic examination, neurologic examination, exploratory surgery, or biopsy may be required. In the case of a deceased stallion it is important to determine the approximate time of death, based on history or physical features such as body temperature, and presence or absence of rigor mortis. Breed association approval for using semen from deceased stallions should be checked by the owner.



PROGNOSIS


Semen quality is influenced by stress, fever, and illness in the stallion. The duration of the stress affects semen quality because of the impact on the spermatogenic cycle; therefore the longer the duration of the problem, the greater the effect on the spermiogram. The ability to collect semen from terminally disabled or dying stallions is influenced by humane welfare aspects in terms of minimizing pain and stress in the individual. The stallion’s pain should be managed with nonsteroidal anti-inflammatory drugs; opioid or morphine derivatives administered orally, intravenously (IV), transdermally, or through an epidural approach. Chemical ejaculation is a viable option for stallions that are no longer able to complete the breeding act or those that have musculoskeletal problems such as limb fractures that prevent the stallion from breeding.


Chemical ejaculation protocols appear to be less successful in stallions that are diseased or highly stressed. This may be due in part to the overall deteriorated health condition of the stallion, medications he is receiving, effects of endogenous epinephrine and cortisol, or a combination of factors.


For this procedure the stallion is fitted with a bag around his prepuce that is secured around his girth. The bag is used for semen collection and needs to be large enough to accommodate the erect penis, because imipramine hydrochloride causes spontaneous erection. Combinations of oral imipramine hydrochloride 0.5 mg/kg followed in 2 hours with xylazine, 0.4 mg/kg IV, have given the best results. The xylazine dose should be titrated to cause good sedation over a 2-minute period. Ejaculation typically occurs either shortly after xylazine administration or after 20 minutes of sedation. The semen is usually emitted in a concentrated state. It should be processed immediately to avoid cold shock.



PRESERVATION OF GENETIC MATERIAL


Options in terminally ill or dying stallions include chemical ejaculation, electroejaculation, epididymal sperm collection, intracytoplasmic sperm injection (ICSI), spermatogonial stem cell transplantation, and harvesting material for cloning.



Electroejaculation


Electroejaculation has been reported in sedated and anesthetized stallions and standing zebra stallions. The quality of the ejaculate obtained by this method has not been reported to be as satisfactory as that obtained by chemical ejaculation or epididymal flushing. An advantage of electroejaculation is that it may be repeated more than once.1


The stallion should be heavily sedated or placed under general anesthesia. Manure should be removed from the rectum. The stallion should be positioned in lateral recumbency. The semen collector should be positioned along the back of the stallion reaching over to steady the penis. A yearling bull–sized probe should be lubricated and placed in the rectum with the electrical contacts facing ventrally. Beginning at the lowest power setting, intermittent electrical stimulation of 3 seconds on, 3 seconds off, using three repetitions at each power setting should be performed until a semen sample is obtained. There will be involuntary leg movement associated with the periods of stimulation. The penis will become erect.

Related posts:

  1. Intrauterine Diagnostic Procedures
  2. Uterine Contractility
  3. Management Regimens for Uterine Cysts
  4. Low-Dose Insemination Techniques

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Jun 4, 2016 | Posted by in EQUINE MEDICINE | Comments Off on Preservation of Genetics from Dead or Dying Stallions

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