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Why Chickens Need Sunshine

Vitamin D is essential for backyard chickens optimal health and egg laying ability.

gray chicken in sunshine

Just like humans, chickens need sunshine too. The UV rays from the sun provide essential Vitamin D to both people and pets.

However, the sunshine also plays other important roles in the life and health of a chicken. Obviously chickens don't wear watches or rely on clocks to tell them when to head into the coop to sleep. That's all based on the sun going down.

Diminishing hours of daylight in the fall also signal to a chicken that it's time to start the annual molt. But most importantly, ultimately it's sunshine that provides fresh eggs.

eggs in basket sitting in the grass

Why Chickens Need Sunshine

According to the FDA, inadequate levels of vitamin D in the diet of a chicken for more than two or three weeks may cause bone weakness, fractures or joint problems, and potentially death in birds not exposed to direct sunlight daily.

Without any sunlight (or Vitamin D supplements), your chickens would stop laying eggs.

Sunshine for Egg Laying

Sunlight is essential for egg laying poultry to stimulate their ovaries to release a yolk and begin the egg laying process. 

Chickens need a minimum of about 16 hours of light per day for optimal laying, ducks need about 14 hours and geese lay best with 10 hours of daylight.

Sunshine for Reducing Pathogens

But sunlight plays another very important role in the health and well-being of your backyard flock. For this reason I try to get my chickens outside from sunrise to sundown every day year round by summerizing and then winterizing my run to encourage them to spend as little time inside as possible.

It's also one reason (among others) that I never recommend a fully (solid) covered chicken run. 

chickens in front of brown chicken coop with green doors

Instead I prefer to see only part of the run covered in solid material - either wood or metal - where you can set up your chickens' dust bath, feed and water so they're protected from the elements, leaving the rest of the run "roof" open to the sun and covered with wire. 

This not only gives your flock access to a nice sunny run, the sun also helps to dry out the run and kill the various pathogens that tend to multiply and flourish in a chicken run. UV rays are the best way to kill most bacteria and pathogens.

In addition to needing a certain number of hours of daylight to lay eggs, chickens and other poultry also need sunshine for another important reason. 

Sunshine for Vitamin D

Like humans, chickens need Vitamin D. And the best way to get Vitamin D is to spend time outside in the sun.

That's one reason why chickens are good for your health! Spending time outside supervising your chickens' free range time allows you both to get a nice dose of Vitamin D.

gray chicken heading back to chicken coop

So Why is Vitamin D important?

In humans and animals, Vitamin D helps the body absorb nutrients better. This includes calcium. So chickens who get adequate levels of Vitamin D will lay eggs with stronger, thicker shells, and also have stronger bones themselves. 

Conversely, a  Vitamin D deficiency in chickens can lead to:

  • thin, broken eggshells
  • low egg production
  • brittle bones
  • wry neck
  • splayed or weak legs
  • trouble walking and standing
  • osteoporosis/rickets
  • deformed keels
  • stunted growth
  • soft or broken nails, toes or beaks

It's also thought that not getting enough sunshine can lead to aggression, feather pecking and overall grouchy chickens. Kind of like seasonal affective disorder, or seasonal depression, in humans?

chickens next to tree

How Do Chickens get their Vitamin D?

In chickens and other birds, their preen gland which is located at the base of the tail, contains oil that the bird spreads over their feathers as they preen. That oil produces  Vitamin D when exposed to sunlight.

That Vitamin D is then absorbed into the body through the skin, much like humans.

However, chickens also absorb Vitamin D through their eyes. Unlike humans who only see the red, blue green color spectrum, chickens also "see" UV rays. Not only can chickens see better than we can, they can see a wider range of color, including UVA and UVB rays. And therefore they can absorb Vitamin D through their eyes.

This skill absorbing the sunlight is what helps to regulate their breathing, signal to them when it's time to molt, and in migrating birds, it tell them when to fly south. 

Although sunlight does shine into your coop, adding to the hours of daylight your chickens need to lay eggs, since UV rays don't penetrate glass, your chickens actually have to be outside to get the benefits of the sunshine.

chickens taking dust baths

Sunbathing Chickens

Your chickens will take advantage of their dust bathing time to also do some sunbathing. You might notice when they are wriggling around and writhing in the dry dirt taking their bath, they'll also often sprawl out, limbs at weird angles, and just lay there. 

I think every chicken keeper has glanced over at some point or another to see one of their chickens sprawled in this pose and assumed they've been killed by a predator! But no, your chicken is just doing a little sunbathing.

chickens dust bathing

Other Sources of Vitamin D

In addition to getting Vitamin D from the sun, it's also possible to get it in foods we eat. Vitamin D is added to chicken feeds, of course. It's also naturally present in eggs, red meat, fish such as salmon, mackerel, sardines and herring, and cod liver oil. There are no plants that contain Vitamin D, although mushrooms do.

Interestingly, or rather, obviously, the eggs from free range chickens will contain more Vitamin D than eggs laid by chickens who never go outdoors.

Some foods such as milk, orange juice and cereals are fortified with Vitamin D.  I personally take a Vitamin D supplement on the advice of my doctor. 

Since we live in Maine, it's pretty common to have low levels of Vitamin D when you live in a northern climate where short days and weak sunlight is common through most of the year.

chickens sitting under trees

How Much Vitamin D do Chickens Need?

Depending on their age, chickens need between 3,000 - 5,000 IU/kg of Vitamin D daily.  This can be easily achieved by allowing your chickens 15-30 minutes outside in the sunshine each day. 

This includes baby chicks. It's one reason why I like to get mine out on the grass (safe and supervised of course!) as early as possible, at least for a bit on warm, sunny afternoons.

baby chicks in the grass

What Happens when Chickens get too Much Vitamin D?

While it is possible for chickens to get too much Vitamin D, it's rare to get too much Vitamin D just from sunlight. 

But it is a fat-soluble vitamin, so it does build up in the body and that can result in too much calcium in a chickens' blood. This is called "hypercalcemia". 

chicken egg with calcium deposits on shell

Signs of a Vitamin D Overdose

Early outward signs of too much Vitamin D and hypercalcemia include small, hard, raised spots on the surface of the eggshell. When scraped off, you'll find tiny holes in the eggshell where the spots were. 

Long-term hypercalcemia can lead to heart and liver damage.  However, it's not common for chickens to get too much Vitamin D merely from being outdoors. It's far more common for  chickens (and humans) to suffer from too little Vitamin D.

Factors Potentially Leading to a Vitamin D Deficiency

  • Confining chickens to their coop during the day
  • Limiting access to natural sunlight
  • Penning chickens in a run that's mostly shaded or covered
  • Feeding chickens excessive amounts of some foods like spinach that contain high levels of oxalic acid

chicken in the grass

So to keep your chickens happy and healthy, laying plenty of eggs with nice strong shells and to also boost your own mood, be sure that everybody enjoys plenty of time outside in the sunshine - year round.

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why chickens need sunshine

Further Reading/Sources

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