Just like humans require supplements, chicken also requires certain supplements that would include minerals and vitamins to make them strong and keep them in optimum health.
The intake for the chickens is essentially dependent on the farm that manages their dietary requirements and is also dependent on the breed of chickens as well. Usually the supplements that are necessary for the chickens include calcium, phosphorus, grit some amount of salt and some vitamins.
Calcium requirement for the chickens varies with their age, weather conditions as well and whether the chicken are the ones that are laying eggs. The hens that lay eggs need more calcium in comparison to those chickens that are bred for their meat.
If the hens don't take proper amount of calcium then they may lay eggs with thin shells or even without shells. Their shells are also prone to breaking extremely fast.
Older hens also need more calcium than the younger ones. In hot weather, the calcium requirement for the hens increases since; the chickens aren't eating enough food and need that dietary requirement.
Ground up oyster shells and ground up limestone are rich sources of calcium intake that the hens can take. However you would have to make sure that dolomite limestone isn't fed to the hens and the chickens, as it can be harmful for them.
Usually some amounts of salt is present in the commercial poultry feed that is given to the chickens. Therefore the chickens don't really require the salt intake. Occasional treats can also contain some amount of salt intake. If you find that their salt intake is less, then you may add small amounts of salt.
In hot weather, ensure that they have plenty of water when salt supplement is given. In the winter, ensure that the water doesn't freeze over; else it can be quite fatal for the chickens. Remember that too much salt intake can be really bad for the chickens as well.
Phosphorus is required for the proper metabolization of the calcium by the chickens.
Since chicken has no teeth, grit must be added to their daily food intake. This is required for the proper digestion of the food by the chickens. Usually grit is stocked and sold by the poultry feed stores and is found as loose grain sand or small pebbles. When the chickens eat the grit, it is stuck in their gizzard. When the food passes through the gizzard it is broken up or crushed into small pieces and aids in the digestion of the food.
Grit acts like teeth in the body of the chicken. Grit is essential part of the meal, even if you are feeding them chicken feed. However the chicken that roam freely on the farm don't require grit as they get their daily share from the grass and the pebbles that are present on the farm itself.
Chickens also have a requirement for the vitamin uptake as well.
Vitamin D is crucial for the hens. Of course the chickens can absorb plenty of Vitamin D from the sun, if not then you would need to add the Vitamin in their food intake. Vitamin D is also present in cod liver oil and is required by the body for metabolization of calcium and phosphorus. Deficiency of this vitamin can cause the eggshells to break easily or the hens to lay eggs with very thin eggshell.
Vitamin A is also useful for the chickens as well. It's especially important for those chickens that are used for breeding purpose. This is the reason that chicken farm owner that have breeding chickens must give ample Vitamin A to their chickens. Most commercial chicken feed will take care of the Vitamin A supplement. The chickens can also get this vitamin from yellow corn and cod liver oil.
One of the B vitamins, this is required by the chickens to ensure that the embryo in the egg reaches it's full stage and hatches as a small chicken. Usually commercial feeds are lacking in this and this needs to be supplemented by chicken breeding farms. The vitamin is usually found in dairy products, yeast; cod liver oil and lots of green leafy vegetables.
This vitamin is essential for the chickens as it helps them to protect against diseases and raises their immunity levels as well. This vitamin is found in fresh greens and wheat germ oil as well.
Ensure that the chicken gets enough of the minerals and the vitamins so that they can lead a healthy and diseases free life.