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Soft Shelled or "Rubber" Eggs - Causes and Prevention

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, basically an egg laid without a shell or with a very soft shell.

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.

A hen needs calcium to form the shell around each 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.

So what causes them?


1) Young layers often lay soft-shelled eggs when they are first getting started. This should stop once their reproductive systems mature and fully develop.

2) Stress can 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.

3) 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).

4) A Calcium deficiency can result in soft-shelled eggs, so be sure you provide the added calcium supplement in the form of egg- or oyster shell.

5) 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.

6) 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.


1) 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.

2) Avoid overfeeding spinach, as 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.

If you do feed the foods in the future, adding some apple cider vinegar to their water (1 Tablespoon of ACV per gallon of water) can help to increase calcium absorption rates.

3) Add some herbs and other greens rich in calcium to their diet.

These include: alfalfa, burdock root, chamomile, chickweed, clover, dandelion greens, horsetail, lambs quarter, mustard greens, nettle, parsley, peppermint, raspberry leaf, rose hips and watercress.

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

Take a Peek at my 'Rubber" Duck Egg  Video

Study on the effects of dietary apple cider vinegar on calcium absorption:

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  1. Lisa,
    Just had to tell you, I finished your book this morning. What a wonderful and informative book. I am especially impressed by your use of natural ingredients which seems to be a completely neglected avenue for so many growers. I have had chickens for a good portion of my life & also appreciate your practical side such as if you don't want your whole yard to look like the coop, you will coop them (nicely of course:) The ice (bundt pan) wreaths are a great idea.
    Again, thank you for all it must have taken to put it all together and get it to the publisher.
    Happy chickens

    1. Oh thank you! I am so happy you liked it. I would love if you left a review on amazon when you have a moment.

  2. As I tossed some overgrown spinach leaves into the chicken pen the other night, I had this nagging thought that maybe I wasn't supposed to be giving them spinach, but I couldn't remember why. I have had maybe one soft-shelled egg in three years of raising chickens, and the girls do love their spinach, so I suppose I will continue to feed it to them in moderation, but along with some apple cider vinegar now. As always, thanks for the good information.