Hello, my name is John Gillam, and I'm a clinical professor of food-animal field services and production medicine, food animal medicine and surgery at the College of Veterinary Medicine at Oklahoma State University. Today I'd like to discuss with you the topic of bovine euthanasia. Well, this is not the most glamorous or fun topic to talk about.
I think it is a very important topic to discuss because there are some challenges that come along with bovine euthanasia, particularly when a veterinarian is not available to perform that procedure. And so there's a lot to discuss and, and a lot of opportunity for us to improve this process. So, first, let's just chat briefly about what our role as a veterinarian is in livestock euthanasia.
And so obviously part of that role may be in just performing euthanasia like we would do with any other species as well. We're often called upon to do that with cattle. We may play a role of counselling a client when that euthanasia is appropriate.
That's not necessarily unique to veterinary, to cattle medicine either, but sometimes other factors come into play where we have to And discuss other options like is euthanasia most appropriate or would salvage be a more appropriate situation in this for this animal. So there's some nuances there that we don't deal with with other species necessarily. And then one area where cattle veterinarians find themselves in a relatively unique situation is the need to train other non-veterinarians to perform euthanasia.
That's really not a big concern with other veterinary species, but for our livestock species, cattle and other livestock, livestock species as well, but today our focus is cattle. And there is often a need to train non-veterinarians to perform euthanasia correctly and humanely, because many times a veterinarian may not be available to perform that procedure. Once the decision is made, that animal needs to be euthanized, and, and ideally we don't want an animal to have to wait until we can get there when the decision is made that euthanasia is the right choice.
So it's important to have individuals on livestock production facilities who are adequately trained and equipped to perform livestock euthanasia, particularly cattle euthanasia, in a humane manner. And so we may find ourselves needing to train owners or sale facilities, feed yard or dairy employees need to be trained. Livestock transporters, truck drivers may be an important source of an important opportunity for training.
People that work the unloading facilities at slaughter facilities need livestock euthanasia training or cattle euthanasia training in particular there because they may often deal with animals that That arrive down or unable to enter the slaughter facility and euthanasia is the only opportunity for them. And even law enforcement personnel often need training on how to properly euthanize cattle when they're faced with an animal that has either escaped and can't be captured adequately or animals involved in a in a vehicle vehicular accident. So there's lots of opportunities that we might find ourselves in where we need to train.
Other individuals to correctly perform euthanasia, and the first step in that is being comfortable ourselves with the different options for euthanizing cattle and how to apply those different options and how to choose which option is best. When it comes to training non-DVMs or non-veterinarians to perform the procedure, the options become significantly more limited, and so we don't have to train a lot of different options, but it's still very important that we train people to properly recognise when euthanasia is indicated and then how to perform that euthanasia once that decision is made. So reasons for euthanizing cattle can be very widespread.
Most commonly, we're going to euthanize animals because of an untreatable illness or injury or when treatment may not be practical or possible. Animals that have prolonged recumbency for a variety of reasons may indicate euthanasia. Sometimes we may have to euthanize an animal that A could potentially enter the food chain but is unable to do so because of a drug withdrawal or food safety residue concern and so that animal maybe can't wait long enough for that residue to clear and so euthanasia becomes the best option there.
Sometimes euthanasia is required for disease control or outbreak situations, and For, for, fortunately for most of us who are just in normal veterinary practise, that usually is not going to be too much of a concern, although we may be called on to assist in those situations. Those situations are typically going to be controlled and conducted by a regulatory veterinarian who either works for the state or the federal government. We may find ourselves faced with natural disasters.
Maybe those can be weather-related disasters. They can be. A vehicular accidents, other issues that may result in a need for livestock euthanasia or cattle euthanasia, sometimes in less than ideal conditions.
And occasionally we may decide that the appropriate step in a diagnostic workup for a particular group of animals is to euthanize a representative or to to try to use those animals for diagnostic purposes. And so euthanizing those animals may be an important step as well. The best resources available currently for euthanasia procedures for cattle and a variety of other species are the AVMA euthanasia guidelines.
These are available free online. Currently, the 2020 edition is the most recent one available. There will likely be a revised edition coming out relatively soon, but as of today, the 2020 version is still the most current, and this document provides a wealth of information on euthanasia covering.
Virtually all veterinary species, all common veterinary species, and the information in their own livestock is very useful and helpful. The American Association of Bovine Practitioners also provides a document that provides euthanasia guidelines, and this is a nice, very concise document that's easy to read, has some good diagrams, and so another, another good resource to have. So these are both good resources to have at your fingertips as you are getting comfortable or reviewing livestock euthanasia or cattle euthanasia guidelines, and both documents are available free on the, on the web.
So when it comes to cattle euthanasia, our options for methods are relatively limited. When we look at the AVMA euthanasia guidelines, the only method that's acceptable under all conditions is barbiturate overdose or pentobarbital injection. That's a familiar technique for most veterinarians because that's what's commonly used for euthanasia of companion animals or horses and livestock in many cases.
So that's a common, common medication, a common practise. Other methods that are acceptable with particular conditions, according to the ADMA guidelines, are the use of a penetrating captive bolt device or a firearm or a gunshot. Those can both be acceptable as long as those conditions are met, and those conditions typically include That we're able to ensure appropriate shot placement to ensure rapid loss of consciousness and rapid death, particularly with a penetrating captive bolt.
There's a need to use a follow-up step to ensure death, and we'll talk some more about that here shortly. And the biggest concern with these two methods is safety, and that safety concern involves not only the animal being euthanized, but also other animals in the area. And most importantly, personnel, the personnel, the operator conducting the euthanasia, as well as any bystanders, particularly with firearm euthanasia, those safety concerns are significant.
So as long as those conditions can be met, the AMA guidelines consider these, these alternative methods or other options. They are equivalent to pentobarbital injection as long as these conditions can be properly met. So really in the US we are, we have 33 tools in our toolbox for cattle euthanasia, and those are Barbual overdose, penetrating captive bolt, and firearm or gunshot, and these are when we're talking about the euthanasia of a conscious animal.
We'll talk about a few other methods here later on that could be applicable to an animal who is anaesthetized or not conscious. So those are adjunctive methods that we might follow up, that we might use as an alternatives would be potentially injection of potassium chloride or magnesium sulphate. These are both concentrated salt solutions that interfere with electrical function of the heart and cause cardiac arrest.
They do not influence consciousness and so they are not considered a humane method of euthanasia for conscious animals because they do not induce unconsciousness first. They simply stop, cause cardiac arrest. Exsanguination is another adjunctive method that can be used, but again can only be utilised for an animal that is not conscious.
And then pithing is a common follow-up step used for after after captive bolt euthanasia. So we'll talk some more about that coming up in a little bit, but the important thing to recognise is that for these adjunctive methods, the animal must be unconscious prior to application of these methods for these to be considered acceptable methods. And then any other method that we might consider using to euthanize the animal.
Are typically considered unacceptable according to guidelines in the US. Those might include blunt force trauma, injection of any other chemicals, using KCL or mag sulphate in a conscious animal, electrocution, any other method that There's a variety of ways to kill animals, but these are not considered humane methods because they do not readily induce unconsciousness, and they could be potentially stressful or painful. So we consider sodium pentobarbital injection or barbiturate overdose injection.
Again, this is a fairly familiar method of euthanasia for most veterinarians. The advantages are that it's very rapid acting. It causes minimal discomfort to the animal.
It's actually an anaesthetic, and so it actually anaesthetizes the animal and then causes cardiac and respiratory arrest. This method is typically the most aesthetically pleasing of euthanasia methods because it is the most sort of peaceful in appearance. And the other advantage is that if we need the brain for diagnostic purposes, this is the preferred method to use because the brain remains intact and undamaged.
A disadvantages of using barbiturate overdose include that it requires an intravenous injection, typically a fairly large volumes when we're talking about cattle. It does require restraint in order to administer that IV injection and the technical skill to be able to administer that IV injection appropriately. Bigger issues though are that this is a controlled substance and is only accessible to veterinarians, so this method is not an option for A non-veterinarian to use and even for us veterinarians to use this, the chemical residue that's left in the carcass poses a significant risk and concern, and we're going to talk some more about that in a moment, but that's one of the major disadvantages of this method is that it leaves a potentially dangerous residue in the animal carcass, and so those carcass have to be dealt with appropriately.
Comparatively, it's a relatively expensive, expensive method of euthanasia. And like we said, it's typically aesthetically relatively pleasing, but sometimes there can be a terminal gas that may be disheartening to some observers, and occasionally in some circumstances, animals could go, can go through an excitatory phase that typically occurs if the medication is administered too slowly and seems to be more common in horses than it is in cattle. Very effective method, very common method, but it does come with some significant disadvantages.
So as we mentioned earlier, pentobarbital is the only fully acceptable method of euthanasia according to the ADMA guidelines, and it is the most common method used by Canadian veterinarians. In a recent survey that was published through AABP. We don't have similar surveys for US veterinarians, but presumptively this will be a common, most common method used in the US as well.
However, In my opinion, again this is, this is my opinion, the veterinary industry should start making efforts to move away from pentobarbital as a primary method of euthanasia, particularly for large animal euthanasia, for a couple of reasons. One is potential availability. Typically availability is not a big concern, but we did experience a period a few years ago where pentobarbital was suddenly not available for a short period of time, and that can obviously raise concerns if we can't get the medication.
And we don't have other methods available or aren't comfortable with other methods of euthanasia, but the big reason that I make this statement is that these environmental residues that are left behind when we euthanize an animal with pentobarbital are a significant concern and I think becoming a greater concern. And so ensuring proper carcass disposal is really, really critical. Another consideration here is that because this is a controlled substance that only veterinarians are able to use, the veterinarian that administers that medication to that animal is potentially responsible for any harm that might, might come from an environmental residue.
So if a non-targeted animal is, is poisoned or injured, by consuming that contaminated carcass, then that liability eventually lies with the veterinarian. So another legal concern there potentially for utilising this method. So because of those concerns, I typically do not use pentobarbital for euthanasia unless I have control of the carcass after euthanasia.
So when it comes to carcass disposal, our options also are relatively limited. At times in the past in the US, rendering has been a reliable option, but as of now, it really is not typically an option for most livestock producers. Rendering services are just not available in most areas of the United States.
If you happen to be in an area where there are multiple feed yards or large dairies, then it may still be an option, but for most producers and veterinarians in the US, rendering is not really an option. But even if it is, If a carcass is if an animal is euthanized with pentobarbital, then rendering no longer is an option for that carcass disposal because there is documentation that the pentobarbital chemical survives the rendering process and can lead to contamination of pet food, and there are reports of pet food contamination with pentobarbital from rendered carcasses that has led to illness and death in pets. And so that's a significant concern.
Composting is becoming a more and more common option for livestock disposal, and it actually works fairly well. It actually works pretty nicely for even small scale producers. So this is becoming a more common option for livestock carcass management.
However, there are a couple of studies that I'm aware of that demonstrate that the pentobarbital compound is quite persistent even in compost piles. The study by Payne etal there. Was using using equine carcasses, but they were able to find pentobarbital residues in the compost substrate and the soil beneath the compost pile for a year after that carcass was placed in that compost pile, and that's as long as the study went.
And, and this study made a comment that there was no significant depletion of drug concentration. The drug concentration was At the end of the study was fairly similar to what it was at the beginning of the study, so the drug was very persistent in that particular study. The more recent study by Lochner et al.
Also used equine carcasses, and they followed that study out for 216 days, and they could still find the compound there. They did find a large scale reduction, so almost 94% reduction in the pentobarbital concentration, but it was still detectable and still present there. They commented in that study that the potential one potential explanation for the difference in concentration is that the pain study just simply used wood chips as their compost material, whereas the Lochner study used equine stall cleanings as their compost material.
So they were wood chips, but also a significant amount of horse manure in that compost material as well. So maybe that different bacterial population was able to Degrade the pentobarbital drug more significantly, but the residue was still there 216 days later. We don't really know what the significance of those residues are, but if someone were to take that compost and apply it to a garden or something like that, it could potentially be a risk for the public health concern.
Burial is the other option that's commonly utilised to dispose of carcasses, and in the US burial is governed by specific rules in each state, and so those rules vary from state to state. So it's important to know the rules for the state that you are operating in, . There are not very many studies that have examined pentobarbital residues from properly buried carcasses, and so that's a little bit hard to draw conclusions there.
We do know that pentobarbital remains in the environment for long periods of time, and there's a variety of studies that have demonstrated that. It has been detected in soil for up to 17 weeks when just the soil was intentionally contaminated and then followed. And there was some reduction in the concentration, but it still was there 17 weeks later, depending on the soil type.
There are case reports of secondary intoxicosis from scavenging, and this one reported here by Kaiser et al. Was a case report of two dogs that were poisoned. One died, one survived after scavenging on an equine carcass that had been partially buried for 2 years.
And so that carcass had been in the environment for 2 years. And it doesn't really describe whether that carcass was just partially buried and exposed or whether it was uncovered at some point, but it had been euthanized two years prior, and these two dogs found it, scavenged on it, and they were actually able to, they necropsied the dog that died and were actually able to get equine hair samples from the stomach of that dog and match those by DNA analysis to the carcass. And so they know that that dog did feed on that particular carcass.
Again, one of those dogs died and 11 was able to recover but was significantly ill for a period of time. And there's other studies that demonstrate that the the pentobarbital compound remains stable for long periods of time in water as well. And so it's a very stable compound that appears to stay in the environment for significant amounts of time.
And so those, those potential residues, I think, raise some concerns. Another carcass disposal method that's used by many animal disease diagnostic labs is alkaline tissue hydrolysis. This is where the carcass is basically dissolved by a solution with very high alkaline pH, and then that effluent is then able to go into municipal sewage systems.
However, to my knowledge, there is no data available describing the persistence of pentobarbital in that process, and we don't, so we don't really know whether the pentobarbital compound survives the alkaline tissue hydrolysis process. So we know that secondary intoxication via scavenging is a concern. We don't really know what the significance of other.
We don't know what other significant concerns are for those environmental residues, but we know this is a relatively dangerous chemical and compound, and so the potential for negative impacts is certainly there. And so I think it's important for the veterinary industry to begin considering taking steps to minimise those residues, particularly with large animal euthanasia when we often Don't have control of the carcass after euthanasia, and that, and the proper disposal of that carcass may be less likely to occur, than it would be necessarily with a, with a small animal carcass. Firearm or gunshot is one of our acceptable or conditionally acceptable conditions or options for euthanasia.
It has significant advantages. One of the advantage is that in the US, at least, firearms are typically pretty readily available and so access to a firearm for euthanasia is usually not too much of an issue. Done correctly, it's very effective and humane.
It does require minimal restraint. We actually do not have to necessarily even touch the animal to perform firearm euthanasia, and we certainly want to be close, and we want to do all that we can to ensure a proper shot so that we get an effective euthanasia with one shot, but we do not have to actually have the animal restrained, which provides a significant advantage in many cases when restraint is not available or an animal is mobile or ambulatory and restraint is not, not available or prudent. Relatively speaking, firearm euthanasia is inexpensive, and it does not leave any significant residue in the carcass for scavengers, except for Potentially lead residue from a lead bullet.
And so for an individual animal carcass, that residue is really insignificant. However, those residues can become a concern when animals are exposed to high numbers of animals that were killed by, by bullets. And so, For example, in California, the US, state law requires the use of non-lead projectiles for firearms, and that's not related to euthanasia, but it's hunting regulation.
And that's because of concerns for birds of prey, particularly California condors, experiencing lead intoxication from scavenging on gut piles from hunter killed animals, and it would take, you know, multiple exposures to be a concern, but that can certainly occur with those scavenging bird species. But from a euthanasia standpoint, that, that chemical residue is, is very minimal to negligent at all. Other disadvantages of firearm euthanasia are the obvious one is safety concerns.
There's those are the most significant concerns with firearm use. Choosing the appropriate calibre and bullet can sometimes be a little bit overwhelming because there's so many options, and we'll talk some more about that in a moment. Firearms do face some legal restrictions, and so there are areas where discharging a firearm is not legal.
And so if a veterinary practise happens to be in a city limit where firearm use is not legal, then this option is not a good option for that location. Aesthetics are a concern, except the aesthetics of firearm euthanasia are certainly not as peaceful as those associated with pentobarbital euthanasia. So it's important to be able to recognise.
The appropriate response of the animal to firearm euthanasia and be able to recognise when that response is not correct or not appropriate so that a follow-up step can be made. So there can be significant limb movement with firearm euthanasia, but that limb movement doesn't necessarily mean anything from a welfare standpoint. But it's important that everyone who's observing that euthanasia understands that.
And recognises the appropriate response of the animal. So the aesthetics can be a concern, certainly not as peaceful as a pentobarbital euthanasia, but beyond that, very effective and very humane when done correctly. The the way the firearm euthanasia works is it applies a variety of forces to disrupt brain function, so the initial response of the animal in terms of loss of consciousness actually is caused by the concussive forces of the of the projectile striking the skull.
And so that initial concussion causes loss of consciousness. And then the bullet has a variety of effects on the brain tissue itself, including A crushing a laceration of brain tissue just from the projectile itself or bone fragments or even fragmentation of the projectile. The entrance of the projectile into the skull is going to cause an increase in intracranial pressure.
It's going to result in haemorrhage, which is also going to result in increased intracranial pressure, all of which tend to significantly disrupt brain function. It's going to cause rotational forces to be applied to the brain, and then the effects of cavitation and shock wave are important for important considerations in captive bolt or particularly firearm euthanasia, but also captive bolt euthanasia. So cavitation is the The increase in wound channel size relative to the actual projectile and shock wave is the projection of energy beyond the furthest depth of penetration.
Of the projectile itself. So even though the bullet may stop at a certain location, the energy that that that bullet is delivering into the brain can actually penetrate deeper into the tissue, more deeply into the brain, and so we can actually get brain disruption to a deeper level than what we got actual physical penetration. The cavitation effect is very significant.
This is an image from a still image from a video. It's available on YouTube. It's just a screenshot of a 45 calibre pistol round being fired into ballistics gel, and you can see the the round there at the end of that wound channel, but notice how much greater the wound channel is in diameter relative to the projectile itself, and that's typically caused by deformation of that projectile.
The bullet kind of forms a mushroom shape on impact with the target. And that very efficiently delivers the kinetic energy of that projectile into the brain. And so if we were to take this, imagine this being fired into a brain inside a bony skull, that huge cavitation effect inside a skull where there's nowhere for the brain tissue to deform or move very effectively disrupts and destroys function of the brain instantaneously, and that's really what makes firearm euthanasia super effective and very humane when done correctly.
There are not a great deal of studies looking into firearm euthanasia as far as selection of the firearm and projectile to use, so the information is relatively limited, but there are several important considerations. One is the firearm type. We may use a rifle.
We may use a shotgun. We may choose to use a handgun, and any of those choices can be effective. And so any of them are good options potentially.
The calibre of the bullet or diameter of the bullet is important, typically because generally the larger the calibre, the more power there is behind that bullet. That may not always be the case, but that generally is a good rule of thumb. And then another important consideration that maybe doesn't get considered as often as it needs to is the type of bullet that is used.
We want a bullet that is going to penetrate the skull adequately, penetrate the brain adequately, and then deliver its kinetic energy into the tissue as efficiently as possible without the risk of that bullet leaving the target animal, potentially causing a safety risk for other animals nearby or personnel. So a typically a soft-nosed, a bullet with a soft lead nose or some sort of ballistic tipped bullet is probably ideal. Hollow points should be avoided because they may not penetrate the skull adequately.
They may. Not have the bullet integrity they need to penetrate the skull may actually the bullet may actually disintegrate on the skull rather than penetrating the skull adequately. A full metal jacket bullet does not distort its shape upon impact to the target and therefore it doesn't deliver its energy as efficiently into the brain.
And it also has a greater potential for exiting the target animal and going somewhere else. And then with a shotgun, we can use a solid slug that works quite well and even pelleted birdshot can be very effective from close range. I know that and that's important to be at close range for that, but it actually can work quite well and actually can be an advantage in some situations because the chance of ricochet or over penetration is reduced, particularly if the animal had to be euthanized in close quarters, particularly like in a, in a vehicle accident.
So the key factors to consider is that the projectile must have adequate energy and bullet integrity to penetrate the skull and destroy the brain while minimising the risk of the bullet leaving the target animal, and there's almost a endless option of choices that could be used in terms of type of firearm, calibre of firearm, and bullet type. But we need to consider these three factors. So adequate energy and bullet integrity are the key factors to make sure that the bullet is able to penetrate the skull and destroy the brain adequately.
But there's lots of, lots of options to do that. And then a penetrating captive bolt is our other remaining method of euthanasia for cattle. The advantages of a penetrating captive bolt are that there's, there's less safety risk than with firearms.
There certainly are some potential safety risks, but much less so than with a firearm because there is no projectile that leaves this device. And so the risk of injury to a other, another nearby nearby animal or bystander is very limited. Captive bolt euthanasia is effective and humane, done correctly.
They are readily available, although not as readily available as a firearm in most areas of the US, but they are readily available, and they are faced with less legal restriction. And so these can be used in areas where a firearm or discharging a firearm will be considered illegal. These are not captive bolts are not considered a firearm because there is no projectile that leaves the device, and so they are not restricted in areas that do restrict firearms.
There are some disadvantages though with captive bolt euthanasia. One is that they require good restraint because we actually have to be touching the device has to be touching the animal's head when it is fired because the penetration depth is limited to typically for most handheld captive bolts, typically about 10 to 12 centimetres of penetration is as much as we can get. And so we need to be actually touching the head with the device when it is fired.
And so that obviously requires good restraint. A shot placement is critical. The captive bolt induces many of the same impacts as a bullet, but doesn't distort shape.
It's shape, and so it does typically destroys the brain less effectively than what a comparable bullet might do. So shot placement is very critical. It's important with a firearm as well, but it's more critical even with a captive bullet.
We typically do recommend the application of a secondary step to ensure death, and we'll talk some more about that here in just a moment. Certainly there are potential safety concerns, although those are less than with a firearm. Comparing a captive bolt device to a firearm, they're actually typically relatively expensive to purchase compared to a firearm on a per animal.
Cost basis for for each euthanasia. The cost is very minimal, but the investment in the equipment can be a fairly substantial investment compared to Many firearms and then certainly the aesthetics are a concern. The aesthetics with Captain Bolt euthanasia are basically the same as that with a firearm euthanasia.
There are non-penetrating captive captive bolt devices available as well. These can be effective on young animals like piglets or lambs or kids or neonatal calves. They, they apply significant concussive force to the brain and small animals with small skulls, that concussive force can be enough to adequately destroy the brain to result in death.
However, in larger animals, these devices may render the animal unconscious, but that unconsciousness is likely to be temporary. And so unless the secondary step can be applied very quickly, there's a significant risk of regaining some consciousness and sensibility, which would be very undesirable from a welfare standpoint. So non-penetrating devices are not recommended for use in adult livestock, particularly cattle and large swine.
So like we mentioned, the captive bullet induces many of the same effects on the brain that a bullet would do. The concussive force applied to the skull is still what results in the immediate loss of consciousness. The destruction, physical destruction of the brain tissue is similar to, although maybe less, the same effects happen that we see with a, with a bullet, but maybe to a lesser degree.
We still get increased intracranial pressure, and the effects of cavitation and shock waves still occur. They're just less than what we see with a firearm again, because the captive bolt doesn't distort its shape on impact and so it doesn't deliver that energy into the brain as effectively as a bullet might do. We were fortunate several years ago to have an opportunity to do some research looking into modifying the captive bolt shot location recommendations and then evaluating those modified shot locations to see if we could comfortably move away from the recommendation for a follow-up step.
And unfortunately we were not able to make that recommendation. We were able to very effectively euthanize animals. We were able to adequately stun every animal in the study.
So in this particular study, every animal was, was shot with a captive bolt in the shot location that you see described there, and we'll talk some more about that in just a moment. Stunning was very, was adequate. Every single animal was adequately stunned and rendered unconscious.
But we did have a small number of animals start to breathe again at some point following the shot, and so a secondary step had to be applied there, so. That this study initially was just to see if we could get away from that secondary step. So we applied the captive bolt, did not apply a secondary step, and just monitored the animals.
And then at any moment where any concerns arose, a secondary step was applied. So you can see that we were right around 90% effectiveness, where 90% of the animals died, experienced cardiac arrest without the application of a secondary step. But a high enough number of them did require a secondary step that we're not, not comfortable recommending that we move away from the use of the secondary step with captive bull euthanasia.
So that recommendation still stands today so far. So our options for that secondary step include, like we mentioned previously, intravenous injection of concentrated salt solutions like magnesium sulphate or potassium chloride. These interfere with electrical function of the heart and cause cardiac arrest.
Exsanguination can be an option. This is what's done in slaughter facilities after animals are, are stunned with the penetrating captive bolt and then exsanguinated to cause death prior to processing. This can be done for euthanasia as well, although it tends to create quite a mess, and so it's not ideal.
We can take a scalpel blade in per rectum and sever the descending aorta, and that will contain most of the haemorrhage within the animal. And so that is a, a less messy way to exsanguinate a bovine. So that's a good option as a, as a secondary step as well.
And then pithing is the method that I tend to use most commonly. And again, that's just inserting something into the hole created by the captive bolt and destroying the brain tissue more thoroughly with that, whatever that device might be, and you can anything from a piece of wire to a screwdriver. I've even used a stiff stalk of Johnson grass one time, but what I typically like to use the most are these uterine infusion pipettes, these plastic uterine infusion pipepettes.
They're pretty rigid but flexible enough that they'll actually go in the hole created by the captive bolt and out the frame of magnum and down the spinal cord a significant distance. So if we run that catheter in and out multiple times, we very effectively destroy the brain stem and proximal spinal cord. And in that case, there's really no, no chance of that animal recovering any kind of conscious, consciousness or sensibility.
They do commercial pithing rods are available, and these are devices that insert into the hole and they actually lock into the skull so they can't be removed, and that is to protect the operator from any exposure to brain or central spinal cerebrospinal fluid. One disadvantage of using this catheter technique is that they are hollow catheters, and so many times CSF fluid will flow out of the catheter during the pithing process. So if there's any reason to have a, a human safety concern from that animal, then this would not be a method to use.
But outside of that, I, I like this using these catheters pretty well. It is very critical that we always, confirm a loss of sensibility prior to applying any secondary methods. So, as we discussed earlier in previous discussion that These alternative methods can only be applied in an animal that is unconscious or anaesthetized.
And so as long as we render them unconscious with the captive bolt first, then we can humanely apply these secondary methods to ensure death. So it's important to make sure that our firearm or captive bolt euthanasia effort has been effective and rendered the animal humane, humanely, sorry, has humanely rendered the animal unconscious or the animal does not have sensibility to any noxious stimuli or stress. And so the way that we do that is by checking a variety of reflexes.
So if the animal is standing at the time of the shot, it should collapse immediately. If it does not, then the shot was not effective. Many times the animal may already be down, and so then we may not see that collapse, but if they're standing, they should collapse immediately.
They should lose all eye reflexes. They should have, especially the corneal reflex. So what we'd like to see is an eye that is centred, has a largely dilated pupil, and no corneal reflex.
And if those signs are evident, like is indicated there in that picture on the top, that's very good evidence the brain is not functioning in that animal, that animal is, is not sensible to any sort of distress because the respiratory centre is located in the brain stem. If we are able to disrupt that, there should be no coordinated respiration. There should be no coordinated vocalisation, and there should be no riding reflex.
The riding reflex can be a little challenging to use in a euthanasia setting. It's used more in a slaughter setting. But certainly if the animal is making attempts to get up, then the stunning and euthanasia was not effective.
I always tell my veterinary students, if you have any doubt whatsoever about the effectiveness of your firearm or captive bolt shot, just shoot again. There is never a reason to not just shoot again if you have a concern. The cost of doing so is very minimal, and the cost of not doing so can be very significant from a welfare standpoint.
So if there's ever any question about whether the animal was adequately stunned and rendered rendered unconscious, then just shoot again. When we consider captive bolt or firearm euthanasia, one of the most critical factors to consider for the technique to be effective is is appropriate shot placement. The goal is to disrupt the brain, particularly the cerebral cortex and the brain stem.
And so we really want to target the brain stem as our ultimate goal because it contains both the A reticular activating system that drives consciousness as well as the respiratory centre, and there are a variety of anatomic descriptions that are published that describe where to place captive bolts shot, and the three most common ones that you'll see are depicted here in these images. The one on the left is the one that we developed in the work here done at OSU, and that is we draw a line from one lateral campus to the other lateral campus and then a parallel line at the top of the pole, and we shoot on midline halfway between those two lines. An alternative described by Dr.
Dell at all is to shoot on midline on a line that connects the ear canals, and then if we look in the AVMA guidelines and AAVP guidelines. What's described most commonly is the use of shooting at the intersection of two lines drawn from the lateral canthus to the top of the opposite ear or opposite horn. It's very important to recognise that those lines are drawn from the lateral campus, not the medial campus.
The previous guidelines described that location as being dropped from the medial campus to the opposite horn. And we've now recognised that that is not an appropriate shot placement for many animals. And so we draw those lines from the lateral canthus or the back of the eye to the opposite ear or top of the to the opposite horn or top of the opposite ear to move that shot location up a little higher on the head.
Just to demonstrate that this is a cadaver head that we used in some of our research. The paint marks on the, on the head are actually drawn from the medial campus, and that bolt track is actually demonstrated in the picture on the right, and it's, you can see that it is completely rostral to the brain, did not impact the brain directly at all with that shot location. And then the other three previously described, the other 3 shot locations described on the previous slide are.
Depicted on there with a different coloured line. So the, the X, the red X is the lateral canthus X. The blue line is the line connecting the ear canals, and then the green lines are the shot location described as halfway between a line across the lateral canthus and the top of the pole.
And you can see that those are all fairly similar in location. And they're significantly more caudal on the forehead or closer to the pole than that medial canthus X. And so drawing that X on the medial canthus, particularly on a Holstein or on any Brahmin influenced animal, is going to result in missing the brain entirely.
So the, the ruler in the picture on the right indicates where the shot would have gone had it been placed at the, at the green dot in the picture on the left. So if we had placed the shot there, it would have directly penetrated the cerebral cortex and the brain stem and been a very effective euthanasia. This image just demonstrates that this is again showing that same shot location, and it appears that the shot was off midline in this animal, but that's primarily because the skin just shifted with the animal laying on the necropsy table.
The hole in the skull is much closer to midline, and you can see there where the bolt track penetrates the brain right through the cerebral cortex and down into the brain stem. So very effective euthanasia there. Other shot locations are described, and the most common one is shooting in the caudal aspect of the pole, and this location can have some advantages because you're not, not having to stand in front of the animal, which can be a potential safety concern for the operator and also can be stressful for the animal.
So if we can euthanize the animal from behind, it may be less stressful for that animal. The biggest Concern with this pole shot location is that the trajectory of the projectile, whether it's a bullet or a captive bolt, must be correct. If it's not correct, then the projectile simply hits the spinal cord and not the brain, which certainly would cause the animal to collapse but not lose consciousness.
And personally, I, I'm OK with this shot location for For a bullet in adult cattle, I don't like it as much for a captive bolt just because there is a lot more soft tissue to get through before we get into the brain and because of the limited penetration depth of the captive bolt, that penetration might be a concern. Although it has been described as an effective method of euthanasia in both calves and adults. The very recent paper by Dr.
Dell looked at various cattle of various ages. And they were effectively able to euthanize animals using this shot location, utilising a single shot with no follow-up step, but That they did have one animal that had to have a 2nd shot because the first shot was not placed properly and the animal did not immediately lose consciousness. And so that's a risk with this position.
So this is an option. We just have to be very careful with the trajectory of the device and it should be aimed at the base of the tongue or even more toward the mouth or nose to make sure that the projectile enters the brain. So we mentioned at the very beginning of the presentation that one of the roles of veterinarians is to train non-veterinarians to properly conduct euthanasia and so That's a very important role.
There just is not a lot of data about that role, but there is enough that we can kind of look and see that, yeah, that is a real concern and we need to be doing, providing that service to our clients. So there's a couple of different surveys that evaluated euthanasia on dairy farms in particular. The study there by Neri et al, the first one listed, relatively concerningly found that 2/3 of the farms in that survey.
Had no one on the farm trained to conduct euthanasia, and again, so that's a significant concern, particularly in large scale agriculture where a veterinarian may not be readily available at any given time. There needs to be someone on that operation who can effectively euthanize an animal when the need arises. Bullwider et al.
Published a survey of US dairy farms and found that the vast majority of them preferred gunshot as euthanasia. Very few use the penetrating captive bullet. Most, most use a firearm, which would, would be expected.
. But concerningly, 8% of those farms used an intravenous injection, but it doesn't say what that intravenous injection was, and it certainly wasn't pentobarbital because these were not veterinarians conducting this euthanasia, these euthanasia, so these had to be producers or employees, and so we don't really know what they were injecting. And then even more concerning, a small percentage of them wouldn't disclose their euthanasia method. And that information just tells me that there's a need for more training on proper euthanasia of cattle, and so there's opportunities there for us to improve animal welfare by making sure our farms have trained personnel on site.
Then a similar survey more recently conducted in Canadian dairy farms found that just about half of producers preferred a gunshot for euthanasia, and at this particular time, 34% of the farms were still using blunt force trauma to euthanize male dairy calves. And fortunately that practise has become very rare now with the popularity of beef on dairy breeding. And those Jersey male Jersey calves in particular, when they are crossed with beef semen, have significant value for the beef industry and so they are no longer euthanized at birth and so that's not much of a concern now, .
But there's still opportunity out there for us to improve animal welfare by making sure that our clients and operations have someone on site trained and adequately equipped to perform euthanasia in a humane manner when when the need arises. There are some alternative euthanasia methods that can be applied if firearm or captive bolt euthanasia is not an option. We've already mentioned the injection of saturated salt solutions to cause cardiac arrest.
That could be either potassium chloride or magnesium sulphate, but these do require general anaesthesia. If the animal has not been Rendered unconscious by a captive bull, we can still use KCL or max sulphate injection, but we have to anaesthetize the animal first, and they have to be in at least a surgical plane of anaesthesia. So my preference is to use high doses of Xylazine and ketamine to induce a deep state of anaesthesia, and then administer the KCL or max sulphate.
Another option is the administration of intrathecal lidocaine. This is described by a variety of authors as a method for euthanizing horses. And it is described as an adjunctive method for horses in the AVMA guidelines.
Although it is not mentioned for cattle in the AVMA guidelines, it is effective and does work, but it does require, again, anaesthesia, surgical plane of anaesthesia. It does not require a lot of lidocaine. Typically about 60 mL injected intrathecally is adequate.
But the real disadvantage of these methods is that again they require general anaesthesia. Which requires controlled substances, which makes them not an option for a non-veterinarian to use. And so in the US at least we're still limited to a firearm or a penetrating captive bolt for non-veterinarians to use from a regulatory standpoint.
So when we think about that, the requirement for anaesthesia prior to application of those methods, the question often arises, is just heavy sedation adequate, or does it, does it have to be anaesthesia? And there's a couple of studies that have evaluated that. This dangerous study here in sheep gave a high dose of Xylazine and then euthanized either by barbiturate overdose, KCL or mag sulphate, and they evaluated brain activity by electroencephalography.
And they found no difference between the euthanasia methods, and that led them to conclude that there was no perceived evidence. There was no evidence of perceived pain or distress in the animals that were sedated and then euthanized with KCL or mag sulphate. However, in cattle, there's only one study that I'm aware of that gave very, very high doses of Xylazine over a short period of time.
And monitored consciousness via EEG. Now these cattle were not euthanized as part of the study, but they were given what would be typically lethal doses of Xylazine and monitored consciousness via electrocephalogram, and none of those cattle achieved what would be considered a surgical plane of anaesthesia. And so that leads us to conclude that in cattle, at least, the use of a sedative alone, even at very high doses.
Does not induce an adequate state of anaesthesia in order to allow us to apply these secondary methods of euthanasia, so we need to Include an anaesthetic agent like ketamine, for example, before we apply these alternative methods of euthanasia, which unfortunately again makes them not an option for a non-veterinarian to use. The AVMA guidelines do specifically state that in cattle the adjunctive method should not be used under Xylazine alone, even at very high doses. So we must include an anaesthetic agent along with a sedative.
So in summary, our options for livestock euthanasia are relatively limited, particularly for non-veterinarians. The options are relatively limited. We're limited to sodium phenobarb, sodium phenobarbital, barbiturate overdose, gunshot, or captive bolt, or if we can anaesthetize the animal, then we could potentially apply an alternative method like KCL or intrathecal lidocaine.
Each option has pros and cons. There's advantages and disadvantages to each one, and so it's important to consider those and choose the one that the operator is most comfortable with and that best fits the given situation, and, and that can vary depending on the situation that the operator and animal are in. The table there at the right is directly from the AABP euthanasia guidelines, and it just gives a nice summary of the pros and cons of each of the options for cattle euthanasia that we have available in the US.
Thank you very much. I hope you found this information useful. If you have any questions or would like further discussion, feel free to email me.
The email is there at the bottom of the slide, and I would be happy to answer questions or discuss this topic further via email. Thank you very much and have a great day.