Please can you explain the difference between the soluble and insoluble grit that a chicken should have in its diet, asks Milly Rees, from Guildford

Charlotte says:

The two types of grit can be confusing. You can buy mixed poultry grit from your local animal feed merchant. This will consist of insoluble grit which are small stones and bits of gravel. This is what your hens use instead of teeth; it will go down through the crop and into the gizzard where it will grind up the pellets and corn. The stones do not dissolve but tumble around in the gizzard, cracking open the husks of grains helping with digestion and allowing the nutrients to be absorbed into the bloodstream. Hens can also pick up this sort of grit from the soil while foraging. The soluble grit is usually in the form of oyster shells but can also be cockle shells or limestone (calcium carbonate). This sort of grit dissolves in the digestive system, giving the bird calcium to produce good egg shells and strong bones. Layers pellets contain this sort of grit in the form of limestone flour but it is still a good idea to put this extra source of calcium out for the birds to peck at ad lib.

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