A good death is one whereby life is ended without pain or distress to the animal, said Dr. J.K. Shearer in a presentation at the Four-State Dairy Nutrition and Management Conference earlier this year. No one likes to do it, but finding the best way to euthanize an animal is important.
Shearer, professor and extension veterinarian at Iowa State University, is chair of the American Veterinary Medical Association’s (AVMA) Panel on Euthanasia Food Animal Working Group, an assembly of experts on euthanasia responsible for the latest revision of the AVMA Euthanasia Guidelines.
Methods commonly used to put down dairy cattle include gunshot, captive bolt and injectable anesthetics. Shearer said all of these methods are considered to be acceptable and appropriate when administered correctly.
In most cases, the most humane and cost effective way to put down a dairy cow is with a firearm.
Handguns should be fired from a range of 2 to 3 feet of the intended target, and calibers ranging from .32 to .45 are recommended for putting down dairy cattle. The .22 caliber handgun is not recommended for mature cattle.
Solid bullets are recommended over hollow points because they are more likely to penetrate the skull. Hollow points are not recommended because they fragment on impact and are less likely to penetrate the skull, which is necessary to cause destruction of brain tissue sufficient to cause death.
Rifles may be required when it is necessary to euthanize an animal from a distance. General rifle selections for euthanizing dairy cattle include .22 magnum, .223, .243, .270 and .308.
Shotguns should be used at a distance of 2 to 3 yards. All shotguns are lethal at close range, but Shearer said the recommended gauges for euthanasia of adult cattle are 12, 16 or 20. The 410 or 28 gauge shotguns may be used on younger animals. He noted one advantage of using a shotgun within close range is that birdshot has sufficient energy to penetrate the skull, but is less likely to exit, which is safer for the shooter and bystanders.
Correct placement of the shot is critical. Shooting between the eyes is too low and causes the bullet to miss the brain, resulting in severe pain and distress. The 2013 Euthanasia Guidelines recommend that the “point of entry for a projectile be at or slightly above the intersection of two imaginary lines, each drawn from the outside corner of the eyes to the center of the base of the opposite horn.”
Another way to find the correct placement of the bullet or captive bolt in a mature Holstein cow is to measure approximately 3 inches down from the center of the poll. For a market weight steer or heifer, one may shorten this distance from the poll to 2 1/2 inches.
He said that the muzzle of a shotgun and other firearm should never be placed directly against the animal’s skull since pressure within the barrel would likely result in an explosion of the barrel and injury to the shooter when fired.
Shearer said that those not familiar with firearms often find a gunshot to be violent or objectionable; nonetheless, when properly applied, “euthanasia by either gunshot or penetrating captive bolt causes less fear and anxiety and induces a more rapid, painless and humane death than can be achieved by most other methods.”
Penetrating and non-penetrating captive bolts are suitable for euthanizing adult or young animals, but use of these devices should always be followed by an adjunctive or secondary step to assure death.
“In general, captive bolt guns, whether penetrating or non-penetrating, induce an immediate loss of consciousness, but death is not always assured with the use of this device alone,” he said.
“An adjunctive method such as exsanguination (bleeding the animal out by cutting the large blood vessels in the throat), pithing (the process of causing additional brain damage by inserting a rod or wire through the hole in the skull), intravenous injection of a saturated solution of potassium chloride (340 grams of potassium chloride per liter), or if unable to apply the previous methods, a second shot by either the penetrating captive bolt or firearm.
“Potassium chloride is very effective but should never be used on a conscious animal,” he said.
Shearer stressed the importance of keeping captive bolt devices clean and in good working order.
“Failure to keep it clean will result in restriction of the bolt,” he explained, which will slow the bolt velocity. Velocity and depth of penetration are the keys to effective euthanasia with this device. Captive bolt guns should be cleaned regularly using the same type of solvents used to clean firearms. Powder charges for captive bolt devices should be stored in airtight containers, particularly in hot and humid conditions.
One drawback of a captive bolt is that the animal must be restrained for accurate placement. Unlike a firearm, the muzzle of the captive bolt must be held firmly against the animal’s head.
“Once the animal is restrained, discharge of the captive bolt should occur with little or no delay so that the animal’s distress is minimized,” Shearer said.
Ensuring that the animal is unconscious is important. Visual indicators of unconsciousness include immediate collapse, brief tetanic spasms followed by uncoordinated hind limb movements, an immediate and continuous absence of rhythmic breathing, lack of a coordinated effort to rise, glazed appearance of the eyes, centralized eye position with dilated pupils and absence of eye reflexes.
The secondary method should be implemented immediately once the animal is determined to be unconscious to avoid possible return to sensibility.
“When conducting euthanasia by captive bolt, preplanning and preparation is necessary to achieve the desired results,” Shearer said.
He also noted that use of a captive bolt gun, along with a secondary method, can be the best and safest option when the task of putting down an animal falls to employees. In general, firearms are more dangerous than captive bolt guns.
Injectable anesthetics such as barbiturates are preferred by some because of the smooth transition from consciousness to unconsciousness to death; however, there are many drawbacks. Restraint of the animal before the injection may be stressful; it can only be administered by a veterinarian; the cost is higher; and carcass disposal is complicated by drug residue. The residue can be a risk to scavenging wildlife, may be considered a soil and water contaminant, and does not break down when carcasses are composted.
Use of electrocution (as with a 110 electrical cord), manually applied blunt force trauma (such as from a large hammer), injection of a chemical not designed for euthanasia or cutting the throat of a conscious animal should not be used.
“I’ve seen these types of things used too often, and it is not ok,” he said.
Shearer stressed the importance of never leaving an animal until you are positive it is dead.
A cow’s heart will continue to beat up to 7 to 8 minutes or more, even when the shot has been properly placed.
“Don’t ever walk off following the initial shot; instead, stay with the animal until you are absolutely sure it is dead.”
If there is any doubt that the animal is conscious, it should be shot again. If the animal is confirmed to be unconscious, one may use any of the previously described secondary kill steps.
Shearer said the most reliable visual signs of death include lack of pulse, breathing and eye reflexes, graying of the mucous membranes and rigor mortis.
“None of these signs alone, with the exception of rigor mortis, confirms death,” he said. PD
Kelli Boylen is a freelance writer in Waterville, Iowa.
PHOTO:These images show the correct placement of the gunshot to euthanize a mature cow. The 2013 Euthanasia Guidelines recommend that the “point of entry for a projectile be at or slightly above the intersection of two imaginary lines, each drawn from the outside corner of the eyes to the center of the base of the opposite horn.” Photo provided by Dr. J.K. Shearer.