Q. Why do chickens need grit?
A. Birds do not have teeth to break down food for digestion. Food is swallowed whole and goes to the crop to be stored and mixed with saliva. The feed then passes to the stomach where it mixes with digestive juices. From the stomach, the feed then passes into the organ called the gizzard. The gizzard contains small stones, which the bird has eaten to help the gizzard to grind up the food for digestion. Nutrients are then absorbed as the feed passes along the intestine. The chicken must swallow the stones that the gizzard requires to grind up the food. Grit is the term for these tiny stones. Granite and cherry stone are two recommended grits. Limestone and Oyster shell are good for shell production, but are not acceptable substitutions for grit because they are too soft.
http://www.tractorsupply.com/content/knowhow/chicks/livestock+care+-+feeding+poultry
Chicks, because they’re babies, need different kinds of food from adult birds. Commercial feed companies formulate chick starter feed with more of the protein that these babies need — 16 to 22 percent. They can transition to adult feed at about 16 weeks.
Never give chicks adult feed. The minerals in it, especially calcium, which is important for laying hens, can severely damage a chick’s kidneys.
Starter feeds typically include medication against coccidiosis, an intestinal disease that can be deadly for chicks. Coccidia parasites, which are released in a bird’s droppings, are common, but keeping pens clean reduces the risk. The dose in medicated feed is so low that chicks get enough exposure to acquire immunity without getting so sick they die.
If you have a specific goal for your flock, such as laying or meat, select the appropriate formulation. Birds being raised as broilers need feed in the 20-22 percent protein range.
For layers, a lay ration with 16-20 percent protein is recommended. Lay ration contains calcium so eggshells stay hard. Supplemental calcium, either through a commercial product, or from crushing shells from your hens’ own eggs, is recommended for older layers, whose eggshells become thinner and more fragile.
Scratch feed is made of whole grains, the kind of tasty seeds that chickens naturally scratch around to eat. It’s not a complete diet — it’s more of a treat — but commercially packaged ones are designed to provide a good addition to the diet.
Chickens don’t have teeth, but they have a gizzard — an organ that contains grit and uses muscular action to grind up feed finely enough to be digested.
Foraging chickens may pick up enough grit — sand and pebbles — to keep their digestion working properly, but grit naturally gets ground up in the digestive process, so chickens must be fed commercial grit to supplement what they manage to pick up.
http://www.tractorsupply.com/content/knowhow/chicks/raising_chicks_chicken_feed
Grit
Ever heard the saying "scarce as a hen's teeth"? That's right, chickens don't have them! Instead they eat tiny pebbles and store them in their "crop". When the food enters their crop, the pebbles grind it up to make digestion easier. For baby chicks, sand, parakeet gravel or canary gravel, available at your local pet store or grocery store pet aisle, will suffice. You can either sprinkle this in their feed or provide it in a small cup or bowl.
http://www.mypetchicken.com/backyard-chickens/chicken-care/chapter-4-caring-for-baby-chicks.aspx
