Causes and Cures for Soft-Shelled and Shell-less Eggs
A soft-shelled or shell-less egg is a rather disturbing thing to find in one’s chicken coop. I have found several laid by my beautiful and sweet-tempered Welsummer hen, Beatrix. She lays infrequently, but when Beatrix does manage to squeeze out an egg, it is either soft-shelled or even shell-less. Aside from being messy egg monstrosities on the coop floor (Beatrix does not care to use the nesting box), these eggs cause me concern about her health.
To delve into the issue of why some eggs come out soft-shelled or even shell-less, it is essential to understand how an egg is made. One cannot consider deviancy before one comprehends the norm.
HOW A CHICKEN MAKES AN EGG
All hens are born with two ovaries, but only the left ovary full develops and produces all of the ova (i.e. undeveloped yolks) that will eventually be laid as eggs. The right ovary does not fully form and remains dormant. Roughly, once every 25 hours, the hen’s left ovary releases a single ovum, though in chickens this is called an oocyte. The oocyte (i.e. a single yolk) once released from the left ovary enters into the oviduct. The oviduct is a long tube-shaped organ that carries the oocyte from the ovary to the cloaca, which is the opening where the eggs come out. As an oocyte travels through the oviduct it is developed into a fully formed egg.
The oviduct organ is divided into distinct segments that perform different duties. The first segment that the oocyte enters is called the magnum; this is where the oocyte is covered with albumen, the protein “whites” of an egg. These egg whites and yolk then continue traveling through the oviduct to the isthmus segment. The isthmus is where the inner and outer eggshell membranes are added over the yolk and whites. These membranes act as a defensive system to keep bacteria out. Next, the egg travels to the uterus (also commonly called the shell gland) segment of the oviduct. The egg with remain in the uterus for a period of time ranging from 18 to 26 hours, during which the calcium carbonate shell is deposited over the egg. Finally, the freshly shelled egg leaves the uterus and moves through the final segment of the oviduct to the cloaca. Just prior to being laid, a protective bloom (i.e. naturally antibacterial coating) is added over the egg’s outer shell. This bloom acts to seal porous holes in the eggshell from being penetrated with bacteria and disease. Here is a LINK to a chart of a hen’s oviduct to help visualize this organ.
THE DIFFERENCE BETWEEN SOFT-SHELLED AND SHELL-LESS EGGS
The terms soft-shelled egg and shell-less egg are often used interchangeably on the Internet. There is however a distinct difference between the two.
A soft-shelled egg has a very thin layer of shell applied to the egg. The effect of this not fully formed shell is a soft feel. More specifically, a soft-shelled egg has a leathery texture and is pliable to the touch. I recorded myself handling one of Beatrix’s soft-shelled eggs, which you can watch below. Though the shell is soft, it is somewhat durable and can be handled.
A shell-less egg is quite different; there was no layer of shell deposited over the egg. The shell-less egg is laid with only the inner and outer membranes enveloping the yolk and whites, and thus is extremely delicate. A shell-less egg is not “egg-shaped” when laid, where a soft-shelled egg will generally be oval. Below is a video recording one of Beatrix’s shell-less eggs. The difference between a soft-shelled and shell-less egg are readily apparent.
CAUSES FOR SOFT-SHELLED AND SHELL-LESS EGGS
There are three common causes of soft-shelled and shell-less eggs. The most common cause is a lack of calcium in the hen’s diet. A tremendous amount of calcium is used to form each eggshell. An eggshell is comprised of 95-97% calcium carbonate crystals. Hens need to have a steady supply of calcium to replace what is lost through egg production. At the first sign of soft-shelled eggs, consider feeding your flock more calcium through either crushed oyster shells (at any feed store) or feeding hens their own eggshells. When recycling eggshells back to your flock it is essential to first bake and crush the shells. This step prevents chickens from recognizing and associating eggshells with food and forming egg-pecking habits.
Dietary imbalance is the second most common cause. Chickens love treats. It can be very tempting to over indulge your birds’ desire for treats and get rid of unwanted leftovers and kitchen scraps. However, feeding too many treats usually results in the birds not eating their layer feed, which is balanced with protein and calcium. Ideally, only 20-25% of a chicken’s diet should come from treats. If you are finding soft-shelled or shell-less eggs in your flock, consider adjusting their diet.
The third most common cause is bullying. Some flocks suffer from terrible henpecking issues. Tormented, subordinate birds are emotionally and physically affected by being constantly attacked. A henpecked bird will often lay misshaped eggs or even stop laying all together due to stress. To a certain degree, chickens must work out the pecking order among themselves without human interference. However, if the bullying in your flock has become vicious and on-going you should intervene. One remedy for serious henpecking problems is to use beak bits on aggressive chickens. A beak bit is a plastic ring that is fitted onto a bird’s beak and prevents behaviors such as feather pecking.
If calcium and dietary deficiencies or stress are not at the root of soft-shelled or shell-less eggs in your hen, then consider some of these less common causes; parasites, disease and poor genetics can cause soft-shelled and shell-less eggs. Lice and mite infestations may stress your hen to the point that she is unable to lay normal eggs or even lay at all. Eradicating parasites can cure soft-shelled and shell-less egg production caused by this issue.
Illness and diseases such as avian flu, respiratory infection, Newcastle’s disease, Egg Drop Syndrome, etc. can also lead to soft-shelled and shell-less eggs. Generally there are no effective treatments for these diseases. Either a disease will clear up in time on its own or it will kill your chicken. A hen that was once ill with these sorts of diseases may not be as hardy a layer upon recovery.
Lastly, genetic defects can sometimes cause soft-shelled or shell-less eggs. A hen simply might have a chronically inflamed or defective uterus that is unable to properly deposit a shell over an egg. Such a genetically deficient hen should not be used for breeding stock. Some chicken sources suggest culling these genetically defective birds. However a backyard hen is often more a pet than livestock and culling may not be palatable.
I fall into this last camp. Through a process of elimination, I suspect that poor Beatrix is genetically lacking. She may not biologically ever be able to produce proper eggs – time will tell. The option of culling her because she is unproductive is not a choice I could stomach. I will never kill Beatrix simply because she is not pulling her weight in the egg-laying department. She still bring me joy to watch and helps keep the bugs and weeds down in the yard – that is payment enough in my book.
Learn more about this topic in episode 30 of the Urban Chicken Podcast, which you can find HERE.