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What Causes Soft Shelled Chicken Eggs?

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Soft-shelled or "rubber" eggs can be caused by a lack of calcium, stress or, a bit more uncommonly, a disease. Learn some of the most common causes and how to prevent them.

The longer you raise chickens, the more chance that eventually you'll collect some odd-looking eggs on occasion. Most times, they are nothing to worry about - just a glitch in production. 

One of the more common 'glitches' is a soft-shelled or "rubber" egg. Which is to say, basically an egg laid without a shell or with a very soft shell.

What Causes Soft Shelled Chicken Eggs?

You might notice a piece of membrane in the nesting box or on the ground or floor of the chicken coop. You might even notice a strand of membrane trailing from your chicken's vent. 

You might  notice a broken egg. Or you might start to notice that the shells on your chickens' eggs don't seem quite as thick any longer and that the eggs crack much more easily.

These are all signs that you might have a hen laying soft-shelled eggs. 

What is a Soft-Shelled Egg?

Soft-shelled eggs often look and feel like water balloons, with the yolk and white covered only by a membrane, not the hard shell, but sometimes there is a shell that is just extremely thin and you can easily crack just by pressing your finger into it.

Calcium Helps to Prevent Soft Shelled Chicken Eggs

A hen needs calcium not only to form the shell around each egg she lays, but also to produce the contractions that help her to lay that egg.

And a diet that consists of good-quality layer feed plus free-choice crushed eggshell or oyster shell normally is sufficient to ensure nice hard shells.

But sometimes that's not enough. Sometimes a hen's body doesn't absorb the calcium she's getting in her diet correctly or there could be a more serious underlying issue.

So what causes soft-shelled chicken eggs?

Common Causes of Soft-Shelled Chicken Eggs

Causes Can Include:

  • Young layers often lay soft-shelled eggs when they are first getting started. This should stop once their reproductive systems mature and fully develop.
  • Older hens often lay thin-shelled eggs since the same amount of shell must encompass a much larger amount of yolk/white than when she was younger (eggs generally get larger as a hen ages).
  • Genetics can play a role in soft-shelled egg formation. Some hens are just predisposed to laying eggs with thin or soft shells. These hens are likely not absorbing calcium as well as they should.
  • Stress can sometimes cause a hen to lay her egg prematurely without the shell. Being chased by children, or harassed by dogs or other predators can be the cause of great stress and fright for a flock. Other sources of stress might include extreme temperature variations, weather, changes in their environment, or the addition of new flock members.
  • Calcium deficiency can result in soft-shelled eggs, so be sure you provide an added calcium supplement in the form of egg- or oyster shell always fed in a separate container from the feed, so each hen can eat as much or as little as she needs.
  • Too much spinach in their diet can cause hens to lay soft-shelled eggs. The oxalic acid in spinach and several other foods can lead to soft-shelled eggs.
  • Not enough Vitamin A can also result in soft-shelled eggs. Vitamin A is important, along with calcium and Vitamin D in the process of forming high-quality eggshells.
  • A Vitamin D deficiency can also result in eggs with soft shells, so allowing your chickens time outdoors in the sunlight year round is important. Hens need adequate Vitamin D for optimal egg production. 
  • Far less common, soft-shelled eggs can be a symptom of such diseases as Newcastle disease or infectious bronchitis. If you are regularly seeing soft-shelled eggs, a vet should be consulted if you have ruled out all other causes. 

How To Prevent Soft-Shelled Eggs

Prevention |

  • Crushed eggshell or oyster shell should always be made available to your flock on a free-choice basis, not mixed into their feed. This way each hen can eat as much or as little as she needs.
  •  Different hens absorb calcium differently, and depending on how good a layer she is, one hen may just need more than another

  • Avoid overfeeding spinachas well as beet greens, chards and citrus fruits, all of which which can interfere with calcium absorption. If soft-shelled eggs are a problem, try cutting those treats out completely.
  • Be sure that your chickens are spending at least part of each day outside. They need Vitamin D for the calcium they eat to be absorbed properly, so a run with a solid roof really isn't optimal for chickens. They should be in the sunlight for the majority of the day if possible. Although chicken feed has Vitamin D in it, every little bit helps, and the sun is the best source for Vitamin D.
  • Be sure you're offering your flock plenty of treats high in Vitamin A. These include leafy green vegetables, squash, pumpkin, sweet potatoes, meat scraps and eggs.

How to Treat a Hen Laying Soft-Shelled Eggs

Because soft-shelled eggs run the risk of breaking inside the oviduct and possibly leading to peritonitis, or getting stuck and causing the hen to become egg bound, treating a hen laying soft-shelled eggs is imperative.

In severe cases, some liquid calcium can be added to your flock's water as an added calcium boost.

Avoid those products with Vitamin D in them because it's actually pretty easy to overdose an animal (or human) on Vitamin D, but liquid calcium with magnesium is okay. Magnesium actually helps with  calcium absorption and is water-soluble, so their bodies will just expel what they don't need.

How to Administer Liquid Calcium:

  • Offer the hen 1 cc of liquid calcium (between 1/8 and 1/4 teaspoon) by mouth 
  • Optimally, she will drink it on her own
  • You can mix it into a little bit of water and see if she'll sip it
  • As a last resort, administer the liquid calcium by eyedropper or plastic syringe by mouth but READ THIS FIRST about giving chickens medications by mouth.

In a pinch, you can dissolve a Tums in some water for a hen laying soft-shelled eggs. Tums are mainly calcium carbonate with some magnesium. 

But they also contain artificial dyes, corn starch, sorbitol, sucrose, and other ingredients you probably don't want to be feeding on a regular basis.

Add Some Calcium-Rich Herbs and Weeds to their Diet

You might wonder how wild birds, waterfowl and other animals get the calcium they need in their diet.

Well, that's easy! 

There are lots of greens and weeds that are rich in calcium. If your chickens free range, they are likely finding and eating some of these one their own, otherwise you can plant or pick them for your flock.

Good choices of herbs and other greens rich in calcium include |

  • alfalfa
  • burdock root
  • chamomile
  • chickweed
  • clover
  • dandelion greens
  • horsetail
  • lambs quarter
  • mustard greens
  • nettle
  • parsley
  • peppermint
  • raspberry leaf
  • rose hips
  • watercress

The Problem with Soft Shelled Eggs

Soft-shelled eggs aren't a problem merely because your hens aren't laying eggs that you can eat, but because a hen laying soft-shelled eggs may more easily become egg bound or suffer peritonitis.  

If an egg breaks inside a hen, she is unable to pass the egg or the egg ends up in her abdomen, she can get an infection called egg yolk peritonitis. 

Symptoms are similar to being egg bound or having water belly and can include ethargy, waddling, no appetite, not laying etc. 

It has to be treated with antibiotics - and probiotics can help as well to rebuild good bacteria. The condition can be cured, but if the hen continues to lay internally, it can be a recurring problem.

So both egg binding and peritonitis are conditions you definitely want to avoid if at all possible. Taking steps to harden those eggshells is imperative! 

Take a Peek at my 'Rubber" Duck Egg  Video

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For more egg oddities, read HERE.