pet grain chicken breaking out eggshell

>For other uses, see Chicken (disambiguation). A chicken (Gallus gallus) is a type of domesticated bird which is often raised as a type of poultry. It is believed to be descended from the wild Asian Red Junglefowl.Chickens are the most common bird in the world. The population in 2003 was 24 billion, according to the Firefly Encyclopedia of Birds. See more at Wikipedia.org...

[erm eggshell is the term for the outer covering of a hard-shelled egg, and some forms of eggs with soft outer coats.The generalized eggshell structure, which varies widely among species, is a protein matrix lined with mineral crystals, usually of a calcium compound such as calcium carbonate. Harder eggs are more mineralized than softer eggs.Insects and other arthropods lay a variety of styles and shapes of eggs. Some have gelatinous or skin-like coverings, others have hard eggshells. Softer shells are mostly protein. It may be fibrous or quite liquid. Some arthropod eggs do not actually have shells, rather, their outer covering is actually the outermost extraembryonic membrane, the chorion, which serves to protect inner layers. The chorion itself can be a complex structure, and it may have different layers within it. It may have an outermost layer called an exochorion. Eggs which must survive in dry conditions usually have hard eggshells, made mostly of dehydrated or mineralized proteins with pore systems to allow respiration. Arthropod eggs can have extensive ornamentation on their outer surfaces. See more at Wikipedia.org...]