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What causes a soft shell egg?

There’s nothing better than checking the nest box and finding a freshly laid egg from one of your hens. 

However, sometimes things may go a little awry and where there should be a nice warm egg, you’re faced with paper-thin shells or no shell at all. 

So, what causes a soft shell egg and what can you do prevent it? We’ll start off by saying that the hens we rehome may well not continue to lay, as is their right – once they land in your garden they’re in retirement of course! 

Naturally though, if your hen is continuing to lay, you’ll want to do what you can to support her and ensure she’s getting enough nutrients to produce good eggs. 

It’s important to say that, even with a soft or missing shell, the taste and quality of the egg inside remains unaffected. You can still whip up some delicious scrambled eggs on toast and enjoy them all the same. 

What is a soft shell egg? 

When your hen comes into lay her eggs are small ‘pullet’ eggs which increase in size as she gets older. When she reaches 26 weeks, she will settle into a normal laying pattern and should lay consistently sized eggs of good shell shape and quality. A laying hen can be expected to lay between 250 and 300 eggs in a laying season. 

At around 72-78 weeks commercial hens are classed as end of lay hens as the number of non-standard eggs may increase as she gets older. A ‘soft shelled egg’ is one that has a membrane but no shell. 

Why does a hen lay a soft shell egg? 

You may find eggs with wrinkles, speckles, target or thumbprint marks or with a soft shell. If an egg is retained in the shell gland for too long, the next ovulation takes place at the usual time, but before the previous egg is laid.  

a soft shell egg

The second egg may spend less time than normal in the shell gland, and the result is a missing egg shell. In such cases, a hen may not lay an egg one day but may lay both a coated and a soft shell egg on the next. 

Here are some external factors which can affect egg shell variations: 

  • Stress or disturbance such as thunderstorms or low flying planes can be enough to desynchronise the process of egg formation for several days. 
  • Inadequate nutrition can also lead to inferior shell quality. The laying hen has a particular requirement for calcium at the time when the egg is in the shell gland. If supplies aren’t maintained, the shells will become progressively thinner and egg production may decline or cease. A calcium supplement such as Zolcal D can be a useful addition to your hen’s diet at this time. Chickens can also get calcium from soluble grit, often called oyster shell grit, and this should be supplied either on its own or as ‘mixed grit’ which includes flint for digestion too. 
  • Temporary thinning of the shell may occur during periods of high temperature (above 25 degrees Celsius) since shell feed intake is reduced. However, in the UK this is not likely to happen very often! 

Are soft shell eggs an issue? 

If your hen easily passes the egg then the fact it has a soft shell is not of major concern. However, if the egg gets stuck the shell can fragment before being laid. 

Soft shell eggs can also be a sign of other ailments such as infectious bronchitis and a shell gland infection.  

If you are in any way concerned about your hen’s health please contact our Hen Helpline on 01884 860084. 

What can you do to prevent soft shell eggs? 

The best way to ensure your hens are getting the best diet is to use a balanced layers’ feed and then supplement this with greens, such as kale, to top them up with other nutrients which maintain good egg production. 

If hens can be allowed to free-range on grass or rough ground, this is much better than any vitamin drink or supplement you can give them. They will be able to pick up a lot of the extra grit, vitamins and minerals that they need and be a lot less prone to health problems as well as soft shelled eggs. 

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