Calcium and Your Flock

Go ahead, grab the label off of your newest bag of feed and read through the ingredients. There is a lot there! We all know that a balanced diet is important for your flock. As a part of any balanced and complete ration that is fed to your flock, you will need to include minerals.
Vitamins and minerals are also on that list of ingredients, but minerals are often overlooked, even though they are vitally important. Nobody wants to see a chicken with a nutrient deficiency. So let’s take a close look at a mineral that is key to eggshell quality—calcium.

Calcium requirements
Calcium is important for growing bodies, but it also a key component of eggshells. The shell is mainly made up of calcium carbonate or CaCO3. The source of calcium is important when it comes to the laying hen. The shell can be made from calcium sourced from the diet as well as from the bones of the laying hen.
That is why feeding the right feed for the right life stage is important. A hen that does not have enough in the way of calcium reserves in her body may not lay many eggs before she ceases egg production all together.

Without proper calcium in the diet, hens may be prone to osteoporosis, and perhaps injury

A growing pullet needs a diet with less calcium than that of a hen in lay. That growing pullet will need approximately 2.75 g/hen/day. A hen in lay must have enough calcium in the diet that she does not deplete the calcium in her own bones in order to put the shell on the eggs.
Changing calcium requirements
Understanding calcium in the diet has been like trying to hit a moving target. It’s tricky! The chickens themselves have changed a great deal since the 1940s and continue to change as geneticists select for different traits. Our understanding of the calcium requirement for the laying hen can also vary based on what strain of chicken has been purchased.
So today, it is estimated that the calcium requirement of the average commercial laying hen, meaning a Single Comb White Leghorn, is 4-5 g/hen/day. This is a far cry from the 1940’s when it was recommended that diets contain 2.27 g/hen/day. And remember, this is not a diet for a growing pullet, rather it is for a hen in lay.
There are even more factors to consider when talking about providing the right amount of calcium to your laying hens. There are differences within your own flock at times if you have hens from different strains or breeds. The size of the calcium particle relates to the solubility of mineral. This ties in to how available that calcium in the diet is to the chicken and the palatability of the feed to the hen. Hens will not eat feed if it does not palatable.
Additionally, is your hen able to adjust her feed intake to partially meet the needs of her calcium requirement? Most of us know that chickens eat to meet their energy requirements first and foremost, but if she meets her energy requirement, and then falls short on her calcium requirement, then shell quality can degrade. And of course, the environment that the bird lives in has a major influence on her feed intake.

Keeping the environment on an even-keeled, comfortable temperature is perfect for a hen in lay. That way she will not need to adjust her feed intake significantly

The hen’s peak time in which she needs the most calcium is during her peak laying cycle. For most hens, their first laying cycle is their best. That is when they consistently lay the most eggs at regular intervals. Their second, third, and perhaps fourth and fifth laying cycles become shorter and shorter. Of course, each of those laying cycles is separated by a molting cycle, or rest in which the hen stops (or seriously reduces) laying. During this rest, the hen replaces the feathers on her body instead of producing eggs.
So how much is too much?
The question of how much calcium is too much calcium has been asked and researched. There are concerns of excess calcium on shell quality, feed consumption, hatchability of eggs, and a few other factors. One of the studies even went as high as 9.48 g/hen/day!

Excess calcium passes through the digestive tract unabsorbed

Actually, hens fed lower levels of calcium ate more feed in an effort to meet their calcium needs therefore making the cost of a dozen eggs increase.
A high quality egg shell, one that will surely deliver that egg to your kitchen or customer, comes at a cost. These minerals can be expensive. Adding them to the diet at the right amount ensures two things. First, that you do not overpay for your feed ingredients and second, that excess minerals are not wasted—and by wasted I mean deposited in the feces and also into your soil or compost. Depending on what types of forage you are raising your poultry on, this can either be a positive or a negative.
Poultry nutrition and diet formulation is quite the balancing act especially when you start to take the soil into consideration. Most people do not think about the soil that their chickens walk around on. Rather, they concentrate on the chickens themselves. (Researchers in Australia are emerging as some of the most forward thinking with regard to pasture management and poultry-keeping as an entire ecosystem.)
Calcium forms
Calcium itself has a couple different forms. Most of us are familiar with the larger particle oyster shell form that can be purchased at many feed stores. There is also the fine granular form of limestone that can be used to supply calcium in the diet.

Both oyster shell and limestone appear to work equally well in supplying calcium to the diet of laying hens

Feeding calcium carbonate in flour form can reduce palatability to the chickens and has the potential to result in a drop in feed consumption.
The funny thing about eggshell quality and calcium is that it is not necessarily all up to calcium to get that shell put on the egg. Vitamin D3 and phosphorous also play roles, and sometimes they can be contradictory roles. If you begin to look at the calcium requirement versus the phosphorous requirement over time, the calcium has been increasing and the phosphorous has been decreasing.
Other potential sources
But what everyone has been talking about of late is insects. Many of the treats we give to our chickens come in the form on insects. There are several different products and companies out there, some large and some small, that supply insects for chickens. Chickens naturally are omnivores and like to eat insects. Who hasn’t seen a chicken chase down a bug only to see that hen snap up that bug in a flash?
Some insects carry with them a ratio of minerals that appear to be promising for inclusion in poultry diets. Again, this is a whole new moving target.
Insects vary in their nutrients at different stages of their growth. There is just not much information out there as to the inclusion of insects or their larvae into the diet. Is there a right amount to include for meeting calcium requirements? My best guess is that more attention will need to be paid to the role of insects in meeting essential amino acids first before researchers look more deeply into calcium. Down the road, it may be exciting to explore insects as a third source of calcium in the diet, even if it needs to be combined with current forms.
But what about breed impact?
Most research has looked at what the calcium requirement is for individual strains of egg laying hens. Next, research has to look at what minimum amount of calcium is needed to meet the hen’s dietary needs.
This ties in to least cost diet formulation. Most often the mistake is made by feeding the wrong diet at the wrong life stage. Pullets, as they begin to transition to an egg layer, have a tendency to overconsume their diet because they are trying to meet their new calcium needs. So when you hens are about 16-18 weeks of age, then you need to switch to a layer diet which has more calcium than the grower diet.
If you know the strain of egg layer that you have purchased (i.e. Bovans, Lohman, Shaver, etc.) then you are in luck! Many of the genetics companies share information on their websites about the specific requirements of their different strains.
If you have a serious interest in formulating your own diets and you have this information available to you, then this information may help you.