A chicken is a bird. One of the features that differentiate it from most other birds is that it has a comb and two wattles. The comb is the red appendage atop the head, and the wattles are the two appendages under the chin. These are secondary sexual characteristics and are much more prominent in the male. The comb is the basis of the Latin name or classification of chickens. In Latin, gallus means comb, and the domestic chicken is Gallus domesticus. The Red Jungle Fowl, ancestor of most domestic chickens, is Gallus bankiva.
There are eight recognized kinds of combs: single, rose, pea, cushion, buttercup, strawberry, V-shaped, and silkie. The chicken has two legs and two wings, a fact that influences housing and management. Heavy breeds used for meat production cannot do more than flap their wings and jump to a little higher level or move more rapidly along the ground. he chicken has pneumatic bones, making its body lighter for flying, although most domestic chickens have lost the ability to do so. The lighter-bodied birds can fly short distances, and some an fly over relatively high fences.
The chicken’s temperature is about 107 degrees to 107. 5 degrees F. Chickens have comparatively short life spans. Some live to be 10 to 15 years old, but they are an exception. In commercial egg production, birds are about 18 months old when they are replaced by new, young stock. It takes close to six months for a female chicken to mature sexually and start laying eggs. Then, they are kept for 12 to 14 months of egg production. After that their economic value declines rapidly, so they are disposed of when they are about 18 months old.
Food prices continue to climb, particularly for high-protein foods, and consumers are constantly searching for ways to reduce their food bill. One way is to include more eggs in the diet. Comparing protein foods on a pound-for-pound basis, eggs cost about 95 cents a pound when large eggs are selling for 64 cents a dozen. It is difficult to purchase any other high-protein food–meat or fish–for this low price. Essential nutrients Eggs are especially valuable as a source of protein. In fact, egg protein is used as the standard against which the quality of other food proteins is measured. One egg contains about 6 to 7 grams of protein.
People of all ages need adequate protein for building and repairing body tissues. The fat in the yolk is so fine that can be digested easily, even by infants. The ratio of unsaturated to saturated fats is about 2 to 1. This is considered very desirable. Oleic acid is the main unsaturated fat. It has no effect on blood cholesterol. Eggs contain vitamin A, the B vitamins (thiamin, riboflavin, and niacin), and vitamin D. All are necessary during childhood and adolescence for growth. Eggs also contain an abundant supply of minerals, such as iron and phosphorus, that are essential for building and maintaining strong, healthy odies.
But eggs are low in calcium (it is in the shell), and contain little or no vitamin C. Individuals on weight-reducing programs find eggs beneficial. To lose weight, calorie intake must be reduced, while maintaining a well-balanced diet. An egg provides good nutrition and contains only about 80 calories. Structure of the Egg The egg is a biological structure intended by nature for reproduction. It protects and provides a complete diet for the developing embryo, and serves as the principal source of food for the first few days of the chick’s life. The egg is also one of the most nutritious and versatile of human foods.
When the egg is freshly laid, the shell is completely filled. The air cell is formed by contraction of the contents during cooling and by the loss of moisture. A high-quality egg has only a small air cell. The yolk is well-centered in the albumen and is surrounded by the vitelline membrane, which is colorless. The germinal disc, where fertilization takes place, is attached to the yolk. On opposite sides of the yolk are two, twisted, whitish cord-like objects known as chalazae. Their function is to support the yolk in the center of the albumen. Chalazae may vary in size and density, but do not affect either cooking performance or nutritional value. A large portion of the albumen is thick. Surrounding the albumen are two shell membranes and the shell itself. The shell contains several thousand pores that permit the egg to \”breathe.\”