A very important aspect of chicken husbandry is making grit available to your birds. Commercial laying hens have a diet containing a type of soluble grit, usually in the form of limestone granules, therefore for backyard hens and ex-battery hens topping up their diet with a suitable grit is necessary. Grit is more complicated than you may think and it is important to supply your birds with a high quality grit containing both ‘insoluble’ and ‘soluble’ components of an appropriate size.
The insoluble component are small stones which travel to the chicken's muscular stomach or ‘gizzard’. As the muscles in the gizzard contract, the stones inside will help to crush food particles, helping the bird to digest particularly harder grains, therefore improving digestion and optimising health. As chickens forage, they naturally select and swallow small stones from the environment, however not all stones are effective. By purposely providing graded chicken grit, stones of the correct size will be made available, not so small that they simply pass through the bird and not so large that they could cause obstructions. Texture should also be considered, smooth stones will be less effective at grinding than coarser stones.
Soluble grit is what it says; it dissolves within the bird’s digestive system, providing calcium carbonate which forms the shell structure. Soluble grit is usually in the form of crushed scallop, mussell shell or limestone granules. Approximately 4g of calcium is needed per day when a hen is in lay. The calcium is taken from the bird’s bones then transferred via the blood stream to the shell gland and eventually to the egg shell. Without having enough in her system, the shell can become weak and the hen can also be at risk of developing osteoporosis (brittle bones). If she has an excess of calcium in her system, it is excreted in the droppings.
As a hen ages, her shell naturally becomes weaker because of the size of the egg mass, meaning the egg yolk and egg white, become larger and the amount of deposited calcium reserved for the shell remains the same, so it has to go further to stretch over the egg mass.
It is unnecessary to mix grit in with chicken feed because birds may not need it at that time; we suggest you provide mixed grit in a separate hopper so your birds can select what they need when they need it. By doing this you are also aware of what amount they are actually eating over a period of time which helps with making sure you have enough available throughout the year.
Growing birds as well as adult birds are partial to insoluble grit, particularly if you are feeding whole grains. Whereas providing hens in lay or about to come into lay with soluble grit and especially the re-homed or older layer soluble grit is essential.