Lights for Commercial Poultry

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Dr. Greg Fraley professor at Purdue University joins me for this episode to give insights into the complicated world of poultry vision and how lighting affects behavior, welfare, productivity, even worker health.  

Transcript

Podcast Transcript Separated by Speaker

Narrator / Intro:

Welcome to the Fowl Frontier, Poultry Science Unplucked, where we focus on practical, research-based insights for commercial poultry production. With your host, Dr. Zac Williams, Extension Specialist with the University of Arkansas Division of Agriculture. Each episode we break down real-world challenges facing poultry growers, from flock performance and nutrition to biosecurity and management, so you can make better decisions on your farm. like one egg said to the other. Let's get cracking.

Dr. Zac Williams:

Alright, welcome back to the show. I've got Dr. Greg Fraley from Purdue. And on this episode we're going to talk about lights and vision and some of the recent research that he's done. And I'm going to let Greg give you some background and tell you about himself.

Dr. Greg Fraley:

Hi, Zach. So I'm Greg Fraley. I'm at Purdue University, as you said. And I'm here in the Animal Sciences Department. I am the Terry and Sandra Tucker endowed chair of Poultry Science. And I am by training a behavioral neuroenterocrinologist. So that means that I study how environmental changes and by environment, it can be like a barn environment management decisions, it can also be the bird's internal environment. So things going on with their own physiology, how these different environmental changes can impact brain chemistry or brain pathways that ultimately control behaviors. And I have mostly worked with feeding, reproduction, and kind of growth variables. But over the last, let's say, 10 years now, I learned that every time I was studying these things in commercial houses that there was always a welfare component. So a lot of my current research is actually trying to better understand what exactly is the neurobiology underlying welfare in our poultry.

Dr. Zac Williams:

All right, good deal. I'm excited to have you on. I've had you on before, but it's been a while. So let's get right into it here. What's, you know, when we talk about lighting for poultry, who knows how much money the industry and farmers have spent on lighting over the years. What's the big deal? Why is lighting such a big deal? Why is it such a big concern for our producers and growers?

Dr. Greg Fraley:

Yeah, well, there's a couple of answers to that. The first and I'd say the most obvious answer is that all of our poultry are seasonal breeders. The vast majority of our poultry species, at least the largest commodities, are long day breeders. That means in order to reproduce, in order to mate and produce eggs, produce sperm, and to breed, they require a long day length. Okay, and by long day length, we typically mean anything over 10 to 12 hours. So that's one very important. So again, they're all mostly long day breeders with the exception of emus. They are short day breeders, but emus are not a very large commodity here in the United States. Globally it is, but not here. And I can't actually decide if I'm happy or sad about that. (laughing) 'Cause they're very, very cool animals, but they're also really, really scary. But the other reason is really the emphasis on poultry welfare. And something that we have known for a very long time but are starting to really focus more recently is that lighting can impact a bird's welfare, can impact their moods, impact their ability to utilize resources, can impact their overall welfare. The problem is we don't really know how, right? We don't understand the mechanisms of all of this, you know, how lighting can affect things like mood. We do know that it does. And we don't really, it's not clear yet what makes for the best type of lighting. There's lots of opinions out there, lots of excellent research on it, but also a lot of contradictory research. So we're still learning, we're still learning.

Dr. Zac Williams:

All right, good, we gotta figure out our mood lighting for chickens, huh?

Dr. Greg Fraley:

Absolutely.

Dr. Zac Williams:

All right, well that's interesting. So we've got long day breeders, except for emus. And I did not know that about the emus. So let's give me a kind of an elevator synopsis of the differences for lighting between like our meat birds, our layers breeders, and then maybe ducks.

Dr. Greg Fraley:

Okay. So for meat birds, they are typically kept on, excuse me, let me back up, for broilers and meat ducks, what we call grow out, they are typically kept on long day lengths. And that is primarily just to help increase their feeding. Our meat turkeys are initially kept on longer day lengths, but because of their very long growth phase, you know, up to 14 to 17 weeks, even longer, whether it's hens or toms, they are kept on a shorter day length. And that is to prevent puberty from happening. Because with puberty, especially the toms, you get a lot of aggression. So light intensity is also another big question with the meat birds, what is best? And from farm to farm, company, you can really find a lot of variability there, but they are typically kept on dimmer lights, we'll say in general. With our breeders and turkeys, it can be quite dim. In our breeders, again, they have to be on a long day length. The differences in lighting are just really all over the board. So there really aren't a lot of or any industry standards or requirements for lighting as yet. So again, it's kind of dimmer light, perhaps in ducks, there's a lot of they're raised in curtain sided barns. So there's a lot of natural lighting, which can be quite bright. Of course, the sun is kind of bright. But And there's a lot of investigations into possibly using colored lights. And again, that's another one of the places that a lot of excellent research on different colored of lights with different species. Broilers, for example, seem to do better with under green lights. Ducks really do best under white lights. If you put them under blue lights, blue lights, that's very, very bad for both grow out and breeders. Bad for their physiology, bad for their behavior and welfare. And turkeys. You saw that video last time, maybe of them just like kind of running around. Yeah, they kind of freaked out. Yeah. And turkeys, again, not a lot of studies. Dr. Karen Schwiedlerner up at University of Scotland has some very cool data about red and blue lights and turkey production and you really need to talk to her about that, how it impacts the eyes, their eyes, how it affects their behaviors. Some very cool stuff that's been published and about to be published on that.

Dr. Zac Williams:

Okay, I'll try to get her illness show then. So it sounds like a lot of nuances between all of our different commercial poultry, either breeds or species, or just all over the place. It's kind of what I'm hearing here.

Dr. Greg Fraley:

Right, and a part of the problem is birds can sense light through multiple different pathways. So, obviously the eyes are one source of lighting or how they can sense or see, if you will, lighting, perceived light. There's also the pineal gland, which all animals have, all vertebrates have, and that helps control our diurnal rhythms, our night day cycles, physiology that changes with night and day, but birds also have these deep brain photoreceptors very well-disturbed for reproduction. But an interesting thing about the brain is there are lots of neurochemicals, right? Lots of neurotransmitters, lots of neuroproteins, neuromodulators. And nothing in the brain only has one job, right? Everything in the brain has multiple effects or outcomes with stimulation. But everyone has always, including myself, has only ever focused on the effects of deep brain photoreceptors with reproduction. And for various reasons, I'm also beginning to start considering them when we're dealing with stress. How light can be a stressor or a calming agent or good for their welfare, bad for their welfare, depending on different combinations, different colors, different intensities. And I'm wondering if that is perhaps another way in which birds, not only how they're perceiving their environment, but how is that brain perceiving that, you know, this may not be the best environment for me. It's pretty fascinating colors or intensities. Yeah, we've definitely come a long way with our lighting schemes and what we know about light, but it still sounds like we have a long way to go before we figure it out. Yeah, sort of.

Dr. Zac Williams:

Our birds are, birds, they're very complicated. They're simple and they're also very complicated.

Dr. Greg Fraley:

Right.

Dr. Zac Williams:

All right, man.

Dr. Greg Fraley:

And it's funny too, I mean, they're essentially living dinosaurs, at least I like to think they are. So they're very, very cool to study. And students especially always ask the same question, why are birds so different? And my typical answer is, well, you know what? They were here first. So we mammals are the different oddballs.

Dr. Zac Williams:

That's an interesting way to look at it. Yeah, but watching that documentary, that new documentary about dinosaurs and how they evolved and evolved. It's a pretty cool documentary. Man, there's a lot to unpack there, which we're not gonna get to today, but a lot of work going on in life. and a lot of different things and just so much that we don't understand about the bird brain and physiology it sounds like Right all right is true. So you've done some research know a lot more than we do That's true. We're getting there though. You've done a lot of research. Yep And I want to talk about a couple of these papers you've done There was one that was interesting to me where you investigated fear response of like some hens in in the light versus dark, right?

Dr. Greg Fraley:

Yes, yes. Yep, if I understand which paper which study you're referring to, we were comparing breeder ducts that were raised from hatch either under 24 hours of constant light versus those that had a light dark cycle, what we call photophase and a scutaphase, scutaphase referring to the dark cycle. And yes, we did find some, a lot of behavioral differences as well as differences in production. Overall, it's sort of the bottom line to that is 24 hours of light throughout a bird's life is pretty bad. That is not good for their physiology and it's not good for their behavior, their welfare.

Dr. Zac Williams:

But what about, and so when we brood them a lot of times, we start them out in like 23 hours of light and one hour of darkness.

Dr. Greg Fraley:

Yeah, yes. So that's a great question. Yes, that is a very common practice and it's my understanding for two or three days. Those first two or three days. So is that sufficient time to actually alter a lifetime of behavior or in development? I don't know the answer to that. And my understanding too, that that practice is based upon a whole lot of people doing it because this is the way it's always been done. And I have yet to find any actual research to show that that is of actual benefit. And my understanding also is the reason for that is so that the birds, again, eat a lot during those days to really help them begin their development, which makes sense, that's a good idea, as well as to make sure that they're finding all of their resources. My guess is it does no harm because it's just too brief of a period. But that's just my opinion. There really isn't any research that I'm aware of off the top of my head to investigate whether or not that's for the birds long-term.

Dr. Zac Williams:

Yeah, that was 'cause your research had said that you had 24 hours of light bad, but that was my question. That was brooding is like, when we do it for, like you said, it's at first like three, three, four days, and it's really just to kind of get used to the house and get them off to a good start. And is that like, is that stressful they just stressed out because they're already in the house and the lighting doesn't really matter that much right

Dr. Greg Fraley:

um well the lighting definitely matters but um whether or not that long period of a photo phase has a deeper impact beyond just getting them habituated and fed earlier on um i i don't know the answer to that so but my study was 24 hours of light throughout their entire life so So for the purposes of this study, we kind of have to do the extremes. And then once we have understand the extremes, then we can go back and look at some of the more subtle changes, such as the rooting.

Dr. Zac Williams:

So you found that it stressed them out. Like what kind of reaction did you see when you had them in 24 hours of light?

Dr. Greg Fraley:

So we did several behavioral tests, fear tests, such as putting them in an isolation chamber, isolation test, also novel environment tests, novel object tests. And the birds under the 24 hours of light were essentially a lot flightier. They were a lot more reactive in the various ways that these tests measure. And so it's very clear that they had a much higher fear response. And honestly, you could just see it every time you walked into those rooms. The birds reacted quite energetically to our presence of walking in the room. And it's interesting too that ducks, a very typical fear response or startle response possibly, is they will tend to circle the room. It's quite impressive to see in a commercial barn, you get 15,000 birds all circling the entire barn. And what's unbelievably cool is they always circle in a counterclockwise direction.

Dr. Zac Williams:

Really?

Dr. Greg Fraley:

Yeah, whether no matter what the orientation of the barn is, where the barn is in the United States, whether it's one of my hens here at Purdue University or commercial sites, doesn't matter. They always circle that way. Dying to go down to Australia, see if they circle the other way. (laughing) Kind of like toilet water. But yeah, so they, and that circling is really bad because they have things like water lines, potentially nest boxes, feeders, and all of these other resources in the barn that they're now running into. And so it's very easy for them to get hurt when they're doing that. So we need to prevent that from happening.

Dr. Zac Williams:

So you're, yeah, so.

Dr. Greg Fraley:

But yes, but the birds under 24 hours of light, this was a very typical behavior.

Dr. Zac Williams:

That's interesting. So that was good, that was one study. Another one you did with some, you've done some work with the paws, right? The pulse alternated. Yeah. All right, I'm going to need you to explain that five.

Dr. Greg Fraley:

Yeah. So that's easy because that's the only level I know. So essentially, these are LED lights, of course, that are programmed. And this is work by a developed by a company that was called "Ziant Lighting" and they developed this and brought me in for doing poultry work to try to understand how the lights were working. And essentially they are programmed to flash, to pulse one and off different colors of light, different, you know, blue, red, yellow, green, whatever. And they do so, these pulses are at the nanosecond interval, so they are completely not perceivable by any living organism. And these, this pulsing light, pulsing colors of light are, seem to have really strong effects, neurologically on on some behaviors and certainly moods. They've done a lot of studies in humans and other mammals and even plants. Of course, plants aren't behaving, but they're growth. And just found really wonderful enough to really make us interested in looking at how they would impact poultry. And in fact, they did. Now there are different recipes and by recipes, I mean different colors of light pulsating at different intervals. What they are, what these different recipes are, is proprietary, so I don't even know. But we definitely found some that had a very clear calming effect on ducks and chickens, possibly improved performance in some cases, or at least more generally, but most importantly did not inhibit or hurt performance production, but definitely seemed to have some benefits in both layer chickens as well as meat ducks. So it was very, very cool. Unfortunately, this company has moved away from the poultry industry a little bit. And we also did have some problems that although there were these benefits to the birds, when you look at the lights, when we humans walk into these lights, it appears to be one color or another. And the recipes that benefited the birds most were colors that the workers did not like working under. 'Cause it was hard to see birds, hard to see resources, hard to see cages, you know, what have you. So that's always a concern, right? We want to improve the welfare of our birds, improve their behavior while maximizing production, but we can't negate the people that work with them. So that became a very interesting balance. But I would love to study these lights some more. But like I said, the company has moved in other directions.

Dr. Zac Williams:

Well, that's too bad. 'Cause yeah, I'd looked up, I'd read some of those articles you did. I wanna kind of maybe talk about one of them a little bit. But you said, 'cause I've had some growers and producers interested in these lights and they've asked about it. I was like, I have no idea. I mean, I know very basic. So the recipe is that, and those are programmed by the company, correct?

Dr. Greg Fraley:

Correct, correct.

Dr. Zac Williams:

'Cause you use like artificial intelligence to program a recipe or is it all like super proprietary?

Dr. Greg Fraley:

It's all super proprietary. So sorry, I really don't know.

Dr. Zac Williams:

That's fine. I was curious about these. And the other, like I said, other people have asked about these. I was like, I have no idea. I was like, I can barely explain how this works. So the recipe is basically like it'll flash blue or green or red or whatever color for so many nanoseconds and then it'll like change. And it just says, does that kind of pattern over and over and over again?

Dr. Greg Fraley:

Yeah, yeah. So there'll be red light flashing, pulsing at a certain interval. And again, these are nanoseconds. Green light will also be doing that, but in a different pattern, red light will be doing that in a different pattern, blue light in a different pattern. So we, all of us living organisms that can perceive light, the flashes are too short, no biological organism can see the on/off. and it just looks like a constant steady light to us. But yeah, the different recipes refer to just different patterns and possibly different colors. Some have more red, some have more blue, some more green. So you could really like--

Dr. Zac Williams:

Just depending on the needs. If you had enough data or whatever, you could really dial that in for a very specific production system it sounds like.

Dr. Greg Fraley:

Absolutely and very different outcomes. Do we want to give cookies more light, but prevent aggression, then we could possibly find a recipe to do that. But again, that would take lots and lots of research.

Dr. Zac Williams:

Yeah.

Dr. Greg Fraley:

To figure that out.

Dr. Zac Williams:

It's too bad the company like-- 'Cause this is-- Sounds like they went a different direction, but--

Dr. Greg Fraley:

Yeah, yeah. They're focusing more on human humans.

Dr. Zac Williams:

I guess, make us better workers, huh?

Dr. Greg Fraley:

Yeah, and sleep better. They have recipes that just make you sleepy.

Dr. Zac Williams:

Oh, that's interesting. So one of your research projects you did with this, you had different recipes and you found that one reduced serotonin turnover and one reduced keel bone damage.

Dr. Greg Fraley:

Yeah, so yeah.

Dr. Zac Williams:

Can you kind of walk us through that a little bit?

Dr. Greg Fraley:

Sure, so serotonin is a neurotransmitter in the brain, very strongly involved with emotions. Okay, so this is the target in human and veterinary medicine with all of the SSRIs, the serotonin selective reuptake inhibitors. So these are drugs like Prozac. So there's literally a trillion dollar pharmacological industry to increase serotonin activity to make us happier, okay, to make us have better well-being. And fewer mood swings, less, just happier, although just keep it simple. So we look, my lab, we look at the serotonin system and we look at serotonin activity in the brain. And so turnover is just, it's a, Some calculations that we do where we're comparing actual serotonin levels in the brain with its metabolites. And what it's broken down into, 5-HEA is the name of the metabolite. And that ratio of metabolites to neurotransmitter gives us an indication of the relative synaptic activity. So when we say that there's a lower turnover that actually means a higher synaptic activity of serotonin and that relates to improved mood in us humans. And this is one of those things that is very highly conserved phylogenetically, evolutionarily, and studies on serotonin activity and mood, emotions, welfare, if you will have been done and everything from humans to all of our pets, farm animals, mammals, and fish, reptiles, I mean you name it, it's been done for decades. So this is very well established. Unfortunately, until recently, it's been pretty much ignored in poultry. So we're making a major effort to turn that around. So essentially when this recipe of Paul's lighting decreased serotonin turnover, that meant it made greater serotonin activity in the brain, which is related to a positive affective state, a relatively more positive affective state, or in other words, better welfare. So that was very--

Dr. Zac Williams:

You had happier birds.

Dr. Greg Fraley:

Yeah, happier ducks. The kill bone damage was, and that was also shown in layers. We also, in the layers, showed that there was reduced kill bone damage, which is, you know, how do you account for that? That's way more complicated. Could they perceive their resources better so that they weren't actually slamming into things, running into things to fracture these kill bones? one possibility. Another possibility is that there was improved calcium deposition in the bones so that they were stronger. That's another possibility. Unfortunately, figuring out that mechanism will require a lot more research and so we'll just see if that can possibly happen in the future. Lots of really potentially very cool items or outcomes with these Paul's lighting and I'd really like to follow up on on these and I'm chatting with the folks who produce them to try to make that happen.

Dr. Zac Williams:

Yeah it's interesting stuff. I've read a little bit about it enough I think I know enough to dangerous. Yeah. But it does seem like it has some real promise for not only the poultry industry but everybody. So that's interesting. But also interesting that you had two different like recipes or colors of lights or whatever and you got two very different outcomes.

Dr. Greg Fraley:

Yes. Yes, that is very interesting and really, really, really cool. And so what that tells us is that there very much is a brain pathway involved with this. And so when light interacts with biological organisms, it's not some magical wizardry stuff. There are very specific photoreceptors. Photoreceptors respond to light just like a hormone receptor responds to its hormone. These photoreceptors are specific to wavelengths of light, specific colors of light. They are more responsive with higher intensity. So the more light that's hitting on the more photons that are hitting your receptors, it's just like a higher concentration of a hormone will have a stronger impact on its receptors. So light works just like that. So that tells us, you know, when one type of lighting works and another doesn't, that we are activating very specific photoreceptors in a very specific way and intensity that is activating certain brain pathways where the other recipe is not. So that's really, really cool. So that strongly tells us that there's a very specific biological mechanism to how these lights work. It's not just some general thing. Now, whether that is through the retina, through the pineal gland, through the deep brain photoreceptors, we don't know yet, most likely a combination of the three.

Dr. Zac Williams:

That's all very interesting. A lot of that is way over my head. I'm glad there's very smart people like you out there doing this stuff, of course. (laughing)

Dr. Greg Fraley:

Well, when I'm doing it, I tend to feel stupid a whole lot. How much I don't know. And we run experiments and we're like in hindsight, wow, we really should have done that differently.

Dr. Zac Williams:

Yeah, I think we always get there. So question, and this is not, I'm gonna, not one that was on our list, but one has come up and people have asked me this. All right, so we put them all these different colors light, all of these color schemes, intensities. Why can't we just give them like white, like, like just give them all the colors?

Dr. Greg Fraley:

Yep, to be honest with you, that tends to be my advice to people. (laughing) I was like, you know what? And if you look at, let's just say example, red light, and you look at probably hundreds of studies around the world that have looked at red light. Well, red light is not all the same. So red light, you know, what we perceive as red light is a range of different wavelengths. OK, I'm going to make these numbers up. But let's say like 700 to 740 nanometers. These are all. And when you look at the different research, everybody's picking a different wavelength. And there is no standard on the intensity, how bright, how many photons of that red light are hitting the birds. So the data, the outcomes, the interpretation is just all over the place, and it's because there is no standard. And if you have one species, or even one string of one species who photoreceptors maximally respond to red light at 720 nanometers, but you give them 715 nanometers, well, you're not going to get an optimal outcome, right? That's just the way the receptors work. They're very specific. But another strain might be at 715. Another strain or species might be at 722. And so we just don't know these things about the physiology of the retina and photoreceptors in every species and in every strain. So it's really hard. And, you know, my bottom line too, is, you know, we all evolved on the same planet under the same sun. So let's just not screw with that and give them all of the spectrums.

Dr. Zac Williams:

Yeah. Give them the whole spectrum. Don't don't keep it simple stupid, right?

Dr. Greg Fraley:

Right, exactly. And, you know, a big question too that that my lab's been starting to work on too is birds are also able to they have photoreceptors specific to ultraviolet light. Now this is not all birds, not all birds do, not all species, but a lot do. And so the question is, do we need to include ultraviolet light to maximize their perception of, or optimize their perception of their environment and even their health possibly, or even moods. But of course the problems, we can't forget the people that work in those barns. So having ultraviolet in your work environment is not such a good idea.

Dr. Zac Williams:

No, not very healthy.

Dr. Greg Fraley:

That causes cancer, glaucoma, all kinds of problems for us. So it's that interesting balance again between our production animal welfare and our human welfare.

Dr. Zac Williams:

Yeah, my graduate student when I was at Michigan State, one of her research projects was, we tried to use ultraviolet light to move hens and like an aviary system. Their reaction to ultraviolet light is, it's pretty intense sometimes.

Dr. Greg Fraley:

Yeah. That's interesting.

Dr. Zac Williams:

Yeah, they, we had, we used the safe ones. What is, oh, I can't remember now, the safe ultraviolet light, anyhow. and we just kind of would like, we would turn it on and they would go nuts. Like it was really good. We could clear out those aviaries in like a couple of seconds.

Dr. Greg Fraley:

Wow, no kidding.

Dr. Zac Williams:

Yeah.

Dr. Greg Fraley:

Wow, if you ever took any videos of that, I'd love to see it.

Dr. Zac Williams:

We do have videos. I'll send them to, I'll show you sometime, but it's, it was pretty crazy what happened. Like it was not what we expected at all.

Dr. Greg Fraley:

I first learned about that I saw it in the barns, I'm like, what a horrible idea. This is terrible. But it turns out that it works just fine if they are managed, if they're managed well. So one, you still have to maintain enough light so you can't have a 800 foot barn with three lanterns. You need to have a lot of lanterns in order to maintain that light for the long day length. And you need to keep the globes clean. So that means probably weekly they need to go and wash all the globes, which of course they're doing by hand. They don't have dishwashers. Well, I guess their children are the dishwashers. But once they start getting soot build up on them, and that really changes the outputs of the lanterns, and that is bad, right? I have publications on that. And what is best is, you know, for the birds, because, you know, going back to the beginning of our conversation about the light cycles, right? So typically when they use the kerosene lanterns, go and turn them on before sunset and they just stay on all night. So now we've got birds with a 24 hour light cycle. Okay, but what's interesting, remember that these are curtain-sided barns, so that light is really, really bright, potentially really bright during the day, but the kerosene lanterns are much dimmer. So are they dimmer enough that the birds rains, So these photoreceptors perceive that as a scotifase as a nighttime. So I'd say obviously not entirely because they're maintaining production. They're still fertile producing fertilized eggs. So obviously production is maintained, so it is perceived as a photo period. But is it or for their welfare, I would say yes. some very important physiological changes happen during the dark cycle. So there's typically an increase in growth hormone, which increases insulin-like growth factor, which is what strengthens our bones, helps our bones grow in immature animals. So could we improve bone health by not keeping them under 24 hours of light? So that's my biggest suggestion, but that's also a lot of work. You don't have light timers for carousel lanterns.

Dr. Zac Williams:

That'd be nice, someone should invent those.

Dr. Greg Fraley:

Yes, absolutely. But the use of those lanterns is fine and it seems to work very well, but they need to be careful about their management.

Dr. Zac Williams:

Okay, that's good. I was, we get a lot of, we get questions about those and a lot of them, I was like, I have no idea. I'm like, I don't know.

Dr. Greg Fraley:

Yeah. (laughs)

Dr. Zac Williams:

Well, good. Well, I think we're gonna get around to the end here. Any, you wanna give us a parting word of wisdom here?

Dr. Greg Fraley:

Well, one thing we've been talking about, the photo phase, the scuda phase, the light cycles, day and night cycles. One of the things that everybody seems to assume is that when we say a dark period, it means absolute dark. And that's typically what happens. There are some people that some companies that will give nightlights, but most don't. And no vertebrate, no living organism on our planet, except for maybe bats, ever experience complete darkness. And so the question is, what kind of nightlights can we give, should we give? And how much light is perceived as actually being dark, a dark phase, right? How much of a drop in light intensity is required to perceive that as a scota phase? And so that's a great question that nobody has investigated yet. It was a very important question. And I had been chatting again with Dr. Karen Schwinn-Narner up at University of Scotland and Dr. Colin Skaens, which pretty much everybody knows, about doing that research. So hopefully next time we talk in a year or two, we'll have some answers for you on that, but very important question.

Dr. Zac Williams:

Yeah, that's interesting. So if I heard that correctly, it's not, your phases are like light and dark phases, our life is like complete sunlight and complete and utter blackness. It's more of a change in light intensity or a noticeable or sensible change in light intensity.

Dr. Greg Fraley:

Right. And so the million dollar question is, we could talk to each other and come up with what you and I think the difference is based on what we perceive, but birds are completely different. There's nothing in our experience that can prepare us for how birds perceive their environments visually and or even physiologically. So figuring that out for birds, for poultry specifically, is a complicated question, as they all are.

Dr. Zac Williams:

Yeah, they don't make it simple for us. Nope. Well, thanks, Greg. It's a good honor to talk to us. Thanks for coming on, and I think this was very informative, as always. And our listeners got something out of it.

Dr. Greg Fraley:

Me too. Thank you so much for inviting me.

Narrator / Outro:

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