Calcium is a critical factor in a flock of laying hens. Too little or too much can cause a host of problems: egg production abnormalities, non-uniform shells, vitamin absorption issues, and metabolic changes. We hope the information below helps you get the perfect amount of calcium in your flock’s diet so they are happy, healthy, and lay perfect eggs!
PART 1: How much do I need?
Calcium supplements like oyster shell or crushed eggshell are recommended at 1 lb/day for 100 chickens when no calcium is present in their diet.
This works out to 0.01 lb/day for 1 chicken. Thus, in a week, each chicken needs 0.07 lbs.
Please note that this quantity is the raw value and assumes that no calcium is present in their feed.
PART 2: Layer Formula
Keep in mind that most commercial feed already contains calcium so we will have to figure out how to properly supplement it.
Let’s do some math:
If a chicken eats 0.3 lbs of feed per day (the commonly accepted amount), this means that it will eat 2.1 lbs/wk.
If 3.5% of this mass is calcium, that means that each chicken is eating 0.0735 lbs of calcium per week just from their feed:
2.1 X 3.5 / 100 = 0.0735 lbs/wk
Notice that this intake figure (0.0735 lbs/wk/chicken) matches very closely with the requirement we found in Part 1 above (0.07 lbs/wk/chicken).
Conclusion: If you are purchasing layer feed that is already formulated for laying hens, you do not need additional calcium for your flock since their needs are being met by the feed.
If you are like us, however, and use a different feed (we like Flock Raiser due to the higher protein content for our bigger birds), please take a look at Part 3 below to calculate the correct amount of calcium to mix into the feed.
PART 3: Non-Layer Formula
First, find out how much calcium is already present in your feed. It should be listed on the bag or available in some way from the manufacturer.
In Part 2, we estimated that each chicken consumes 2.1 lbs of feed per week.
Our feed contains about 1% calcium by mass (this amount depends on your feed formula).
That means each chicken is getting 0.021 lbs of calcium per week from their feed:
2.1 X 1 / 100 = 0.021 lbs/wk
From Part 1, we found that each chicken needs 0.07 lbs of calcium per week. If they obtain 0.021 lbs/wk from their food, then the difference is the supplemental amount we should mix into their feed:
0.07 – 0.021 = 0.049 lbs/wk per chicken
Multiply this figure by the number of chickens in your flock to figure out how many pounds of calcium supplement you should mix into their feed each week.
We have 20 chickens so every week (Saturday morning when we refill the feeders), we mix 1 lb of calcium into their feed:
0.049 X 20 = 0.98 lb/wk
You can measure this amount with a regular kitchen scale. Be sure to tare out the scale with the container holding the calcium before you start measuring.