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.
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.