Hens work hard to provide us with their daily eggs. Making egg shells takes a lot of calcium. The more eggs they lay, the more calcium they need. If a hen doesn’t get enough in her diet, her body will steal calcium from her bones to make the egg shell. This leaves her bones very brittle. You may think of Osteoporosis which women sometimes get as they age. Hens often have that same problem.
The egg shell that a hen lays is 95% calcium by weight. In one year the amount of calcium put into her shells can equal 20 times the amount of calcium that is contained in her bones. In order to stay healthy and create strong egg shells, she needs to consume a large amount of calcium in steady intervals.
The most recognizable sign of calcium deficiency is thin shelled eggs or even eggs laid without a shell . Lack of calcium in the diet can also lead to soft shell eggs which look rubbery. This can also lead to egg binding which can be fatal in hens. Rough spots and wrinkles on the shells are another sign of low calcium. The egg shells should look hard and smooth.
Ground oyster shell is the most common supplement to increase the amount of calcium in a hen’s diet. Oyster shell is inexpensive and lasts a long time. It does not spoil or go bad. Oyster shell is eaten by hens and the shell dissolves in the gut. It is not the same thing as grit. Grit aids digestion by grinding up food in the crop. Oyster shell has nothing to do with digestion. It also does not stimulate egg laying. It simply provides the mineral calcium to the hen.
To lay well, a hen needs 16% crude protein . Most grains range 7-12% protein and are low in certain essential amino acids. High amounts of protein can contribute to more frequent ovulation in a hen. Make sure that you are giving your hens a balanced feed with the correct nutrients and protein. Most of their food should come from a nutritionally balanced food. If you give them treats or let them free range you can be upsetting this balance.
Most hens start to lay at about 20 weeks. Wait until the hen has actually laid an egg to begin giving them oyster shell supplement. Giving it too early can damage the young pullet’s kidneys. Oyster shell should be given free choice in a separate bowl so they can eat as much as their body needs. Laying hens who aren’t getting enough calcium can produce weak or irregularly shaped eggs. This issue can also cause slow laying or even problems like egg eating because they are so desperate for the calcium they need.
How much calcium a hen needs is an individual issue and all hens are different. Some breeds lay eggs every single day. Other breeds take more time off, such as silkies. The hen’s bodies will prompt them to eat the oyster shell as they need it. If you don’t see them eating it, they may not need it
Do not mix the oyster shell into the food. This can force them to eat too much calcium which can damage their kidneys. Feed it to them in a separate bowl or even scatter it on the ground. Some commercial feeds contain calcium, but it is often not enough for typical layers, especially if they have access to table scrapes and treats.
In order for the hen to be able to absorb the calcium, two nutrients seem to affect it the most. These nutrients are Phosphorus and vitamin D3. Phosphorus is easily found in grains. D3 come from sunshine so you want to make sure that your hens have exposure to sunlight. Powdered vitamins added to the water will help with this.
I have found oyster shell to come in many different sizes. Some pieces are so large they can barely swallow it, down to basically nothing but powder. The ideal particles size of supplemental calcium ranges between 2 mm and 5 mm. Larger pieces of calcium carbonate take longer to digest than smaller particles and are more desirable. Hens seek out large particles of oyster shell late in the day before the period of shell formation occurs. Shell formation usually occurs during the night. Too much calcium will give the eggs an extra coating of powdery calcium around the entire egg or you will see calcium deposits around the shell.
Hens do best when fed a balanced crumble or pelleted diet, especially an all-flock diet with oyster shell in a separate bowl on the side. Meat birds should be given a separate feed. Birds that eat other things besides their layer food such as free range foragers or birds that get extra treats need the extra calcium from oyster shell.
Oyster shell is not for pullets that haven’t started laying eggs yet. Wait until they actually start laying eggs to give them the extra calcium. Chickens who are not laying will get enough calcium in their daily feed for normal calcium use. When they are laying they need four times as much calcium as a non laying hen. Giving additional calcium to chickens who are not layers is detrimental to their health. This would include roosters, cockerels, and older hens no longer laying.
Oyster shell should never be mixed with the food. Just leave it out in a separate bowl. They will instinctively know to take it when they need it. Do make it available all year round. If they aren’t laying as much in the winter, they will just lower their intake of it.
There are other forms of calcium you can use. Limestone is a rock that contains calcium. If you live in an area with limestone gravel they may naturally pick some up. Some people save egg shells and offer these back to the hens. Remember that a hen’s own shells will not provide enough calcium if she doesn’t have other supplements. Bake the shells first in a 350 degree oven for 10 minutes to kill any bacteria that may be present. Crush them finely so that they do not look like egg shell, otherwise you are teaching the hens to eat their own eggs.
For more tips and tricks for raising outstanding silkies check out our weekly silkie blog at VJPPoultry.com. VJP Poultry is an NPIP and state inspected hatchery located 30 miles north of St. Paul. We hatch out silkies all year long so we always have stock available. Like us on Facebook to get weekly updates on what we currently have for sale.