Mary Allen
The additional feeding of grit is often not given enough attention in chicken feeding, but it is vital. Two grams of this additional feed are necessary per chicken and day.
Chickens don’t have teeth to shred the grass pecked in the run. Only in the gizzard is the eaten meal broken down by small stones. The quartz grit takes over this task. Shell limestone provides enough calcium, which is necessary for eggshell formation. The shell limestone can be added to the laying hen feed. It is also possible to administer quartz grit and shell limestone in a separate automatic feeder. There, the chickens meet their own needs right away.
For growth, poultry needs a lot of calcium, also known as lime. This is the most important mineral in poultry farming. It builds bones. Once egg production has started, a hen needs around two grams of calcium per laid egg. On laying days she takes one gram from the feed and the second necessary gram she takes from her bones.
In the book on poultry nutrition and feeding, Carl Engelmann goes on to say that the eggshell becomes thinner with low-lime feed. Observations have shown that hens completely stop laying after twelve days if they are completely deprived of lime. Up to this point, around 10 percent of calcium has been removed from the body for egg production. Lime requirements are high during the laying period and therefore the shell quality can decrease towards the end of the laying year because there is not enough lime. In the case of thin-walled eggshells, the reason could be a feeding error or a metabolic disorder in the hen.
Chickens can get calcium from oysters, mussel shells, or lime grit. All three forms are coarse and slowly soluble. The granulation is best adapted to the age of the animals. For pullets, it should be one to two millimeters and for laying hens it can range from two to four millimeters.
All of the above points about the quality of the eggshell show the need for free feeding of shell limestone and quartz grit. This is also described in the guide to exemplary poultry farming from Kleintiere Schweiz.