Dr Sebastian McBride will present "Recognising Clinically Depressed Horses” at the Horses Inside Out Conference at Loughborough University on the 17th/18th February 2024. In this blog article we learn all about the man behind the incredible work.
Dr Sebastian McBride PhD is the programme leader for Postgraduate Courses in Animal and Equine Science, Department of Life Sciences at Aberystwyth University. Present projects include equine sleep, equine depression, equine stereotypies and equine cognition.
We are so pleased that Intelligent Horsemanship allowed us to share this article here. It was orginally published in Intelligent Horse magazine in Autumn 2023. Learn more about Intelligent Horse Magazine and the amazing work they do here: www.intelligenthorsemanship.co.uk
Sebastian left Northern Ireland at 17, and after some traveling, he took an undergraduate Zoology Degree in Liverpool. This was in the late 80s early 90s and like many young people with a deep interest in animals, mainly dogs at that time, Sebastian thought he wanted to be a vet but after doing some work experience with “probably the most unenthusiastic vet in the whole of Ireland” that changed his mind and influenced Sebastian to look at other career choices…
*Young people take note. Always do work experience before making hard and fast career choices!
Sebastian’s Northern Irish parents were artists which is likely to have influenced his decision to take an artistic sabbatical that produced the book and exhibition at the National Library at Aberystwyth in 2006 called ‘Portrait of the Horse’ using photos he’s taken from his worldwide encounters with the horse.
“I knew there were some animal science courses, but they tended to lean a lot more towards agriculture. So, I went with zoology which is a generic animal-based degree, and which ticked the boxes for me.”
He then worked in France for a year milking sheep and taking out horse treks before taking up his PhD in Edinburgh vet school on the physiology of abnormal equine behaviour. “The whole three years was basically on crib biting” and he became really interested in what was changing in the animals’ brain in order for it to manifest this ‘odd’ behavior.
“I've always been very interested in how stress affects the brain, and how that can then lead to changes in behavior as a result of those brain changes. The PhD was the starting point for that. And then I came down to Aberystwyth, took on the lectureship position, and had Andy Hemmings, who you know as my PhD student, and we started to investigate some of those brain changes”.
(Dr Andrew Hemmings has presented at a number of Horses Inside Out conferences in the past and presented the brilliant seminar on Training the Brain which is available in the Horses Inside Out Academy. If you are interested in behaviour and training of horses then this is a must watch for you! LEARN MORE HERE)
“We spent a lot of quality time in horse abattoirs. Not the most pleasant places to be taking out horses’ brains and we looked at those neurophysiological differences between the stereotypic and the non-stereotypic phenotype. As a result, we got a much greater working knowledge of different regions of the brain, and in particular, the basal ganglia.”.
The Reverse Engineering of the Vertebrate Brain
When I came out of that lectureship, I did the art sabbatical but wanted to get back into academia, but not as a full lectureship, so I did some post doc in research positions. There was an opportunity here in Aberystwyth in the computer science department, they had a project, which was called The REVERB project, which is an acronym for the Reverse Engineering of the Vertebrate Brain. They were specifically interested in using the mechanics of the basal ganglia, as an architectural basis for developing autonomous robotic systems.
They were looking for a biologist or neuroscientist to come in with a working knowledge of that part of the brain as a way translating basal ganglia mechanics into something that could be used in a useful way to develop robotic systems. I was still very much the biologist, but I worked alongside the software and hardware engineers to help engineer the robotic system.
How do we distinguish between stereotypical behaviours being caused by animal boredom or animal stress?
“The problem with these words, is that they are quite vague in their operational definition. It's very broad terminology. Stereotypies in horses are largely coming out of the behavioural needs of the horse not being met. A horse stuck in a stable, not being able to do those things that are important for a horse; be with other horses, run around and eat for prolonged periods of time; if they can't do that, then you could imagine that would culminate in a state of frustration, which in many ways is stressful. So, frustration is a form of stress."
The Use of Language
But also, an animal that is in a situation or an environment of very low stimulation (where behaviours can’t be performed), is also going to be an animal potentially experiencing boredom. So much of the terminology in that respect is interchangeable but probably the global term stress is the most useful.
An interesting point about stereotypes is that they seem to derive from different motivational states. For instance, weaving is very locomotory. It’s linked with not being able to access food, but also wanting to be with other horses or not been able to perform locomotory behavior. Whereas crib biting is much more linked to a continued motivation to eat. Thus, the type of stereotypy that the animal develops depends on the motivation state of the horse.”
Have we decided yet whether horses’ copy?
“It's an interesting one, in that there's always a lot of anecdotal evidence to that effect. People will say ‘my horse picked the stereotypy up from its neighbour’. There is a research paper that suggests that a stereotypic neighbour does have an influence on what that other animal is doing. But all of that has definitely got to be in the context of the animal already being in a state of stress where genetic predisposition is also going to be very important."
It seems the horse is the only species where we try to physically prevent stereotypies. Many owners still use anti cribbing collars and anti-weaving bars are standard fixtures in a lot of stables. The work that I did early on would tend to suggest that those devices are quite stressful to the animals in that they will raise plasma cortisol levels.
People may be trying to stop these behaviours being performed from ‘a clinical sequelae perspective’. Meaning the performance of these behaviors is doing some harm to the animal. There's a window of opportunity early on in the animal's life, to stop the behavior forming or becoming ingrained and that’s the time to really try and facilitate the behaviors that the animal is unable to perform before the stereotypy develops and becomes established. Once it becomes established it is very difficult to get rid of.
Crib biting also seems to be linked to the weaning time. So, six months is when you see quite a high abundance of crib biters developing, but then it's more like 56 weeks for the locomotory stereotypies to start to develop.
Stereotypic or Clinically Depressed?
The early work I did with Andrew Hemmings was based on a previous rodent model. They had taken two different strains of mice and exposed them to stress. One strain became stereotypic, and the other strain became clinically depressed.
They took the brains out of those animals, and they looked at dopamine systems. A very basic description of the results is that stereotypy animals had an up regulation of the dopamine system and the clinically depressed animals had a down regulation of the dopamine system. We were very excited about this at the time as it helped us to identify that both genetics and dopamine are really important for the development of stereotypy.
This became the basis for all of the questions that we were asking about equine stereotypy. We studied the brains of stereotypic and non-stereotypic horses and looked at those dopamine systems to see whether it was up regulated in similar way to what had been observed in the rodent model. And this turned out to be the case.
I was also interested in the mouse strain that had been exposed to stress but had not developed stereotypic behaviours. Their dopamine system was down regulated and associated with a state of reduced behavioural output that we would call clinical behavioural depression. In this respect, I have always wondered if there is the equine equivalent of that clinically depressed state?
In simple terms, if you're going into a yard and there are 100 horses and there are maybe only 10% that are stereotypic - does that mean they are the only ones that are stressed? What about the other 90% of those animals? Maybe some of those are still experiencing stress, but they're reacting to that stress in a diametrically opposite way, with a down regulation of the dopamine system and a down regulation of behavioural output?
Behavioural depression is much more difficult to get a sense of in the horse. For example, if you look at that horse in a stable with its head down is it in a state of drowsiness? Is it sleeping or just resting? Or is that an animal in a state of behavioural depression? It’s much more difficult in that sense to clinically identify it. And that's something that we are working on at the minute.
Standard measures for depression are things like ‘anhedonia’ - an inability to have the sentient experience of pleasure. For example, you’ll find with depressed mice or depressed people, if you get different levels of sucrose solution, they're not very good at differentiating those different levels, or they tend to have less preference for sugar versus maybe, a neutral substance. So, their ability to be able to experience reward becomes dampened. The level of REM sleep can be affected in the depressed state. So that's also something we're interested in and the amount of beha
vioural expression. The general activity level of the animal, the amount of movement of an animal within a stable, for example, can again be quite indicative of whether it's normal or whether it's depressed or whether it's in a sort of hyperactive state. So those are some of the markers that we're interested in at the minute.
How are you sleeping?
Is your horse sleeping well? And how would you know?
We've published a number of studies trying to work out what is normal equine sleep. If we can get a good sense of normal equine sleep and then what is abnormal equine sleep, then we can investigate what factors in the animal's environment might produce abnormal equine sleep.
When I'm saying abnormal, I’m referring to animals that are in a constant state of sleep deprivation. We know as humans if we consistently don't get good sleep that it has all sorts of negative emotional and cognitive effects and also motor effects as well. So, you can imagine from a performance horse perspective that ensuring good equine sleep is going to be absolutely critical. If you ask most leisure riders how much sleep their horse is getting, most do not know, nor how much sleep their horse should be getting.
There are two types of sleep, REM and Non-REM sleep and the horse is interesting because it can achieve non-REM sleep standing up. Questions we currently need to answer include; what is the proportion of time that the animal should be standing in a sleep state versus lying in the sleep state.
How much variation is there in time spent in different sleep states within a normal population of animals? Once we've answered those questions, we will be able to look at factors that are affecting equine sleep.
So far, we've been looking at the effects of different lighting, different forms of bedding, novel environments, all of those things we might take for granted as being part of the normal horse environment that could actually be very impactful on their sleep.
Keep Exercising - Brain Derived Neurotrophic Factor
There is a lot of evidence for the value of exercise. We have a big sports science and health department here at Aberystwyth University. They are very interested in the beneficial effects of exercise and are trying to understand why exercise is beneficial, especially with regard to stroke patients. What can exercise do for that damaged brain? A substance called BDNF, Brain Derived Neurotrophic Factor is really good at repairing the brain whether it’s normal or damaged. Brain Derived Neurotrophic Factor is produced more by the body during exercise, and this is considered to be the link between exercise and its beneficial cognitive effects.
I adapted an ovine (sheep) cognitive system for use in horses to allow us to use different cognitive tests to probe different parts of the horse's brain. If you're interested in the functioning of the hippocampus, for example, you can set up specific memory-based tasks that test that part of the brain. Or, if you're interested in the relationship between the basal ganglia and prefrontal cortex, then you can carry out another sort of test called the two-choice discrimination reversal test. We've got the system up and running, and are developing these methodologies to allow us, in a very standardised way, to specifically test functional and integrity of different parts of the horse's brain.
An example of this has been work that I have done with Andy Hemmings at Royal Agricultural College and Matt Parker at the University of Surrey. We had identified neurophysiological differences in stereotypic horse in a very specific part of the brain called the striatum. This part of the brain is responsible for motivation, acquisition, learning, action, outcome learning, and also habit formation. Having identified those neurophysiological differences, we could then make predictions about how stereotypic horses would perform differently in the context of learning and cognition. We then tested those predictions and found them to be true.
The original neurophysiology work I did with Andy had great value, but it did involve having to go to abattoirs and take brains out, as well as being limited in the ability to behavioural profile the animal before it got to that point in the abattoir. Our new way of working using these cognitive probes is hugely advantageous in this respect.
Dr Sebastian McBride will present "Recognising Clinically Depressed Horses” at the next Horses Inside Out Conference taking place on the 17th/18th February 2024
[For full details and to purc hase recordings of the talks, go to www.horsesinsideout.com/c24]
Thanks again to Intelligent Horsemanship for sharing this article here. It was orginally published in Intelligent Horse magazine in Autumn 2023. Learn more about Intelligent Horse Magazine and the amazing work they do here: www.intelligenthorsemanship.co.uk