If you’ve got laying hens then you’ll be familiar with all the issues that could affect eggs: declining production, hidden nests in the woods or issues with quality: soft-shelled, bumpy, odd shapes or thin-shelled eggs. I occasionally get a few of the latter. They’re problematic because eggs with brittle shells are easily broken in the nest box and that can encourage egg eaters. And if they do make it intact till collection time I don’t sell them to my customers because they are more difficult to hard boil.
Egg shells are mostly comprised of calcium carbonate. The process of laying eggs drains calcium from the hen’s body. Their comb, wattles, legs and ear lobes will fade as the calcium leaches out so it must be replaced. Calcium deficiency is the most common reason for thin-shelled eggs, but as you’ll see it’s not the only one.
Just like with many chicken health issues the cause could be any number of things. Here is the laundry list of various impacts that result in thin-shelled eggs, which may help you to do a bit of detective work to figure out what’s going with your own hens.
Continuous Egg Production: hens that are forced by artificial lighting to lay for long periods without a break. Hens need opportunities throughout the year to rest and not be pushed to lay more.
Egg-laying Times: Eggs laid before 10 a.m. are usually formed at night when blood calcium concentration is low and shells are thinner. If hens are fed early in the morning their blood calcium concentration is high when their eggs laid in the afternoon and tend to have thicker shells. (Note: I read this, but haven’t found it to be true in my experience).
Age: hens over the age of two are considered past their prime; young pullets just starting to lay and not on Layer feed can deplete their bone reserves of calcium.
Thyroid Issues: can affect the absorption and utilization of calcium.
Molting: Physiological changes during the hen’s molting process can make the egg shell thinner and increase the number of broken eggs.
Stress: disrupts nerve and endocrine gland function, which affects calcium formation of the egg.
Overweight: Obesity or fatty liver issues impact egg quality.
Poor Ventilation: may cause ammonia build up and respiratory issues. Hens can lose carbon dioxide, resulting in insufficient calcium carbonate ions and the absorption of calcium.
Temperature: Temperatures above 32°C make it difficult for chickens to dissipate heat and affects feed intake. You’ll need to find strategies to cool your coop and help your birds avoid heat stress.
Water: Water is critical – and more important than food – for your birds’ health. It helps to digest, absorb and transport nutrients and metabolites, expel waste and regulate body temperature. Both a chicken’s body and egg are mostly made of water, so ensure they always have plenty of fresh water.
Overcrowding or Flock Dynamics: can lead to competition for food and water; pecking, bullying and stress.
Calcium Deficiency: Eggs are mostly made of calcium carbonate so if your hens are lacking calcium it will have a direct impact on shell quality. If you have a mixed flock (i.e. different ages or males and females) keep everyone over the age of six weeks on All Flock or Grower feed and offer supplementary calcium (oyster shell, crushed egg shells or calcium rich foods) separately for the layers.
Non-layers don’t need and, more importantly, can’t utilize the excess calcium which can lead to kidney issues, gout and death. If you have a hens-only flock you can give them Layer feed and supplementary calcium, if required.
Calcium Size: Larger particles of calcium (.5 cm) will be stored in the gizzard for longer and released more slowly than smaller particles, so ensure your oyster shell or crushed eggshells isn’t too small.
Vitamin D Deficiency: hens deprived of natural daylight can have issues with eggshell quality. Fish liver oils, canned tuna (no salt), egg yolks, greens, grains and germinated pulses are other good sources of vitamin D.
Excess or Too Little Phosphorus: provide quality balanced feed. If you are making your own understand the calcium, protein and phosphorus requirements.
Moldy Feed: Improperly stored feed can become mildewed which can cause liver and kidney issues. Store feed properly to prevent moisture, never give moldy feed.
Lots of chicken keepers – especially new ones – have high expectations of their hens to produce an egg a day. Not only is that unrealistic, it’s unhealthy for them. There are many impacts on production, some that can be remedied and others, not. As your hens age it is normal for their eggshells to becoming thinner and more brittle. If you’ve got younger birds with these issues try to narrow down the potential cause and tweak something in your management which might improve their eggshell quality.
Credits: High Top Poultry Equipment; Manitoba Department of Agriculture Featured Image: Frugal Chicken