Interesting study and implications for coop/run design: Increasing vitamin D in chickens/eggs

[TooCheep]

There are multiple threads on BYC about vitamin D supplementation for chickens- generally concentrating on their feed. This is important both for their health and for vitamin D levels in the eggs that they provide us. Vitamin D is important both for our bone health and disease resistance.

However, there is surprisingly little on how light/UV exposure naturally generates vitamin D. I just read an article that states that at least 6 hours/day of UV-B exposure results in at least a 3-4x increase in vitamin D in eggs from indoor-raised chickens. This has significant implications for factory farmed egg nutrition, but also somewhat for backyard flocks.

My run has good access to light all year long. However, there is a privacy fence about 10' away on the east side and half of the west side of my run has a tarp all year for wind/rain protection. The other half has clear plastic for the same function. The tarp and fence both affect how many hours of direct sunlight they have. Having good shade is particularly valuable in summer, but is far less valuable in winter. I'm going to convert to clear plastic for the whole side and can still add a tarp for shade in summer when there is a lot more light and heat. This conversion will have minimal cost. It is possible that this might also extend their laying season somewhat.

Shorter article from Science Daily: https://www.sciencedaily.com/releases/2019/06/190624111502.htm
Full study report published in Poultry Science (I only skimmed this): https://www.sciencedirect.com/science/article/pii/S0032579119480395?via=ihub

This info will not affect all of us equally. Some with fully free-ranging chickens and/or good 4-side light access can probably ignore this info for their backyard flocks. Anyone else might want to think about their setup while still providing at least some shade area all year long.

 

[raingarden]

Read up how "clear" plastics affect availability of UV light.

 

[TooCheep]

Read up how "clear" plastics affect availability of UV light.

I'm afraid that info is hard to dig out. All of the searches I did were far more likely to find "uv resistance" or "uv stabilizers" which is created by plastic additives, which isn't even a concern for me. I did read that those can block up to 95% of UV rays, but not all plastics have these additives.

I use clear plastic polyethylene drop cloths to create a winter enclosure. They are locked in by furring strips and are easily removed in the spring. The plastic is then discarded. I left the plastic on the windward side this year to block wind/rain.

The drop cloths would not normally encounter extended sun, so I do not know that they are UV resistant at all. Can you offer any more info?

 

[Krugerrand]

My understanding is that UVB will not penetrate glass, so I expect it will not penetrate plastics as well. Also from what I have read, you need the sun at 50-degrees or higher to get UVB rays. In my parts of SW PA, that means no UVB from mid-September to mid-March. (DYODD)

 

[TooCheep]

My understanding is that UVB will not penetrate glass, so I expect it will not penetrate plastics as well. Also from what I have read, you need the sun at 50-degrees or higher to get UVB rays. In my parts of SW PA, that means no UVB from mid-September to mid-March. (DYODD)

I did. Unfortunately, that's exactly what I'm having problems finding info on. There are applications where people want the plastic to be resistant to UV-caused breakdown and others where they don't want UV to penetrate clear plastic or to selectively block the UV. Those are all controlled via chemical additives.

There are tons of links on these subjects such that I haven't been able to find anything about (a) are they ever not added and (b) how much UV blockage is there without additives. That seems to indicate that UV can penetrate clear plastic, but I have not been able to locate anything that specifically addresses it.

 

[Geena]

I did. Unfortunately, that's exactly what I'm having problems finding info on. There are applications where people want the plastic to be resistant to UV-caused breakdown and others where they don't want UV to penetrate clear plastic or to selectively block the UV. Those are all controlled via chemical additives.

There are tons of links on these subjects such that I haven't been able to find anything about (a) are they ever not added and (b) how much UV blockage is there without additives. That seems to indicate that UV can penetrate clear plastic, but I have not been able to locate anything that specifically addresses it.

Look at clear plastic sheeting made for greenhouses.

 

[BarnyardChaos]

Watching and learning.....

 

[TooCheep]

Look at clear plastic sheeting made for greenhouses.

Thanks. That provided some help. It turns out that most do include UV resistance because that also makes them break down more slowly, but some people intentionally purchase "open" plastic for a more natural light spectrum. I suspect that untreated polyethylene would fit into that category or if anything would be better, but I still don't have anything concrete on it. Still looking...

Does Greenhouse Plastic Block UV Rays?

Greenhouse plastics that allow UV light to enter the greenhouse provide a more natural growing environment for plants, as UV rays are present when growing outdoors.

These plastics do degrade far more quickly, but many growers intentionally use them for the natural growing environment that they provide within the greenhouse while still being strong and sturdy enough to maintain growing conditions and protect the greenhouse plants.

Also, I'm not sure this plastic discussion is even covering the critical point. That is the risk of working from summaries of a study rather than going to the original article. From the study in the original post, full spectrum light also had a beneficial effect, but UV-B specifically had a greater one. It won't change what I'm doing, unless I can identify a better type of plastic for the job. I still think they will get some vitamin D benefit and may lay for a few more days each year at a low cost.

However, what I'm hoping for is that some people may read this thread and design their coop/run a little differently to allow more light access.

Edit: Here is a direct link to the graphs in the study.
https://ars.els-cdn.com/content/image/1-s2.0-S0032579119480395-gr1.jpg

 

[Krugerrand]

I did. Unfortunately, that's exactly what I'm having problems finding info on. There are applications where people want the plastic to be resistant to UV-caused breakdown and others where they don't want UV to penetrate clear plastic or to selectively block the UV. Those are all controlled via chemical additives.

There are tons of links on these subjects such that I haven't been able to find anything about (a) are they ever not added and (b) how much UV blockage is there without additives. That seems to indicate that UV can penetrate clear plastic, but I have not been able to locate anything that specifically addresses it.

Again, I haven't looked into this in a long time. But, UVA will go through glass ... thus you can get sunburned through glass. But UVB will not. So, something that generalized "UV" may or may not apply to UVB rays.

 

[raingarden]

I'm afraid that info is hard to dig out. All of the searches I did were far more likely to find "uv resistance" or "uv stabilizers" which is created by plastic additives, which isn't even a concern for me. I did read that those can block up to 95% of UV rays, but not all plastics have these additives.

Some UV radiates right through plastic sheet, some reflects off the plastic, and some is absorbed by the plastic. The part that is absorbed is what is degrading the plastic. But, I can't find a percentage of UV that makes it through either.

Out of a dozen small cages and pens, we only have one with a solid roof. That's only because corrugated plastic is a much cheaper roofing material. But, the main thing limiting sunlight in our yard is the tree canopy and there's not much we can do about it.