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Poultry Science Sample LessonPT103 Basic Avian Anatomy and Biology 
MAIN IDEA: What do I need to know about the bodies of chickens and other birds? Birds are a unique form of life. They are unique in the way they reproduce and grow. The structure and biological processes of birds are all important to the way chickens, turkeys and other poultry species can be used to produce eggs and poultry meat. Any understanding of poultry science and poultry production requires knowledge of the anatomy and the biology of avian species. An avian is a warm-blooded vertebrate, commonly known as a bird. The avian class includes some 10,000 species in 27 orders. A good way to understand the avian is to look closely at its parts. It is not at all the same as a cow or a pig. The study of those parts and the way they are put together is called anatomy. Biology is the science of how those parts work to help a bird or any other organism live, grow and reproduce. In short, anatomy is the study of the structure of a body, while biology includes the study of the life processes used by the body. In this lesson you will find a brief overview of the anatomy and biology of chickens. THE PARTS OF A CHICKEN The anatomy of a chicken includes a study of both external and internal parts. Both can influence the way birds grow, reproduce and need to be managed. Comb: The chicken comb is the first thing you may notice about these unique birds. The comb has a purpose. It serves as a cooling system. Chickens do not sweat to provide cooling. Instead, birds are cooled by blood that flows through the comb and wattles. Warmer blood from the body flows into the comb and then returns to the interior parts of the body as it cools. The comb is at the top of the chicken head and is one of the unique features of chickens. Wattles are two appendages under the chin. Wattles are more prominent in male birds. Many avian species do not have combs or wattles. The scientific classification of chicken is Gallus domesticus. It includes the Latin word "gallus," which means comb. There are several types of combs that help to identify different breeds and varieties of chickens. Feathers: Chicken feathers provide insulation that helps to keep birds warm and protects the bird's skin from getting wet. Feathers help birds fly or glide. While domesticated chickens have lost much of their ability to fly, some lighter breeds are able to fly short distances. Feathers grow from areas of skin sometimes called "feather tracts" or "pimples." These begin to appear in an embryo at about the fifth day of development. When chicks hatch, they are covered with down. Feathers begin to grow in a few days, covering the birds in four to six weeks. Another feather growth begins at two to three months of age, and a final growth develops when birds become sexually mature. Hens lose feathers (molt) naturally about once a year as part of their natural reproductive cycle. They molt when they stop laying eggs. The feathers do grow back and they start laying eggs again for the next reproductive cycle. Poultry breeders, however, have developed strains that can molt while continuing to lay eggs. Scientists have also discovered that control of lighting can prevent molting in laying hens. Feather patterns and color are used along with skin and leg color, body shapes, combs and beaks to help identify breeds and varieties of chickens. Neck and back feathers can also be used to determine the sex of adult chickens. The feathers of males have pointed tips and are shinier then those found on females. Female feathers have rounded ends. Feet, legs and wings: Chicken feet, legs and wings have an influence on how chickens are housed and managed. Chicken legs have scales and most chickens have three or four toes with claws used in scratching. Domestic chickens have wings but cannot fly well or at all. Heavy breeds used for meat production can do no more than flap their wings and jump. Lighter birds can fly short distances and clear fairly high fences. Skeleton: The chicken skeleton is light and strong, designed to help birds fly. Some bird bones are hollow and serve as a part of the respiratory system. Another unique feature of the chicken skeleton is the formation of "medullary bone" in hens during egg production. The female hormone estrogen stimulates medullary bone production, filling the bone marrow cavity and providing a source of calcium for egg production. Hens draw on bone calcium when producing eggs at a high rate. Muscles: Chicken muscles provide both "white meat" and "dark meat." The white meat comes from white fibers that contain very little myoglobin. Myoglobin is an oxygen-carrying protein of the muscle cells. The chicken breast has mainly white fibers. Meanwhile, leg muscles contain more red fibers with more myoglobin. Red fibers receive a larger supply of blood than white fibers and are capable of greater aerobic metabolism, which is the process of producing energy by burning carbohydrates and fats. Many muscles contain a mixture of different types of fibers. BIOLOGICAL FUNCTIONS Many parts of the chicken anatomy, especially the internal parts, are closely related to biological functions such as respiration, digestion and reproduction. If a bird is to grow and reproduce, it needs to breathe to provide a source of oxygen. It also needs to eat and digest sources of energy, protein and other nutrients. Eating and digestion: Birds eat and digest their food in ways that are quite different from mammals. Chickens do not have teeth. That is why the old saying "as scarce as hen's teeth" is so very true. Chickens do have an efficient beak they can use to pick up and take in kernels of grain and other foods, but they cannot chew. From the beak, food is then propelled backward to the esophagus where it is carried to the crop, an enlarged part of the esophagus at the foot of the neck. The crop serves as a temporary storage bin. It allows the chicken to eat its daily ration in a short period of time and digest it later. The storage time depends on the type of feed. A full crop of grain may require 24 hours to empty, while a full crop of mash will take less time. From the crop, food moves to a glandular organ called a proventriculus. This organ is similar to the stomach of other animals, because it produces a gastric juice containing acid and enzymes. In birds, however, there is very little mixing of food in this stomach-like organ. Instead, the food moves on to another organ called the gizzard, or the ventriculus. This muscular organ with a hard lining is where food is ground and mixed with the gastric juice. Traditionally flock owners have provided chickens with grit to help improve feed digestion. Grit is provided with small stones that a bird stores in its gizzard. Grit helps the grinding process and increases the digestibility of certain feeds. However, today many commercial producers do not use grit because they feed a ground meal that can be digested by the bird's digestive juices. From the gizzard, food moves into the small intestine where most of the breakdown of food occurs and the nutrients are absorbed. Chickens have a poorly developed sense of smell. This has an influence on the way they select the food they pick up to eat. They mainly use taste, vision and sense of touch. A chicken is able to recognize shape, size and color and can feel material with its tongue and mouth. In addition, its sense of taste is not the same as that of humans. Chickens seem to recognize tastes in water better than in dry feeds. These factors are all important in selecting feeds and preparing rations. Chickens may learn to prefer certain food ingredients. This may make it more difficult to change feed mixtures. Chicken appetite is stimulated by an empty crop, an empty rectum, cold temperatures and the sight of food. Respiration: Respiration rates of chickens are higher than those for larger animals. In general, the smaller the kind of bird, the faster it breathes. For example, a hummingbird breathes more times a minute than a chicken does. The male chicken breathes about 18 to 21 times a minute and the female about 31 to 37 times per minute when they are not under stress. Chickens have a number of air sacs that help to make the body lighter for flight. These sacs also are an important part of the respiratory system. They provide a reserve for birds and provide a more efficient exchange of gases. This greater efficiency, however, has a disadvantage. It may make birds more susceptible to respiratory diseases. It allows respiratory infections to spread beyond the lungs into the abdominal cavity and bones. Heart: The heart of a chicken has four chambers and the circulation is the same as in the heart of other animals. The chicken heart rate is very rapid, about 200 to 300 or more beats per minute. In smaller birds, it is even more rapid -- up to as high as 1,000 beats per minute in the canary. Body temperature: Body temperature of the chicken is quite high. The normal range is about 105 to 107 F. This is why chickens remain comfortable at higher temperatures, up to 100 F at a relative humidity of 65 percent. They may have maintained this trait from their jungle bird ancestors in Southeast Asia. While the comb helps birds keep cool, birds cool themselves mainly by respiration, especially at higher temperatures. They will pant when the temperature is too high. Birds also will spread their wings when they feel too hot. Some chicken breeds, such as the Leghorns, can tolerate heat better than others. Heat management is more important for baby chicks than for older birds. Chicks cannot control their body heat very well. Brooding temperatures are critical. Social order: Social order can also cause problems for poultry producers. Chickens have a well-developed social pecking order. Birds at the bottom often suffer from injury and a lack of feed and water. This is a difficult problem in close confinement housing. Poultry scientists and producers use the term "cannibalism" to describe excessive and harmful pecking. The practice of beak trimming to blunt the sharp point of the beak has long been used as a means of reducing the harm that can be done by aggressive birds. While the practice is described as similar to clipping your fingernails, it has become highly controversial among animal rights activists. A number of things can be done to help prevent cannibalism. Introducing new birds is always a risk. It leads to a period of social upheaval as a new pecking order becomes established. Mixing groups of roosters is highly risky and likely to stimulate destructive fighting. Periods of stress can also cause problems. Birds are more likely to peck at each other when they run out of feed or water, are cold, or are placed into strange groupings. Once an individual bird is injured or starts to bleed, it is likely to become a pecking target of other birds and will soon be killed or will need to be culled. Beak trimming is the most effective way to prevent pecking and cannibalism or to control this behavior once it has developed. Individual aggressive birds may be treated. However, for effective prevention, it is best to trim the beaks of all the birds. Life span: The life span of the chicken is quite short. With its fast heartbeat and high rate of metabolism, it should be no surprise that the bird burns itself out quite rapidly. While it lives, it converts the grain it eats into meat and eggs at a highly efficient rate. Some chickens live to be 10 to 15 years old. They are the exception. Broiler chickens go to slaughter at a very early age. Commercial egg producers replace bird at about 18 months of age. It takes about six months for pullets to become mature hens and begin laying eggs. Hens are then able to produce eggs for 12 to 14 months of egg production. After that, egg production and economic value of the hen declines rapidly. BOTTOM LINE: This lesson material covers a few important and interesting highlights of the anatomy and biology of chickens and other birds. There is much more you can learn from other sources, included the listed Internet Resources. In addition, you will find more about avian reproduction in the next two AgEdNet.com Poultry Library lessons in this series, PT104 Poultry Reproductive Systems and PT105 The Avian Egg, Fertilization and Embryo Development. EXERCISES: Discuss the following in class and/or write a report with answers for your teacher. 1. Review the sites listed under Internet Resources to acquaint yourself with additional sources of information on the anatomy and biology of avian species used in poultry production. Which of the sources did you find most interesting and most helpful? Explain why. 2. List anatomical features or biological processes of chickens covered in this lesson that you feel can have implications for the way poultry flocks are managed. Explain and discuss how each feature or process you have selected influences poultry management. 3. From what you have learned in this lesson, explain why the legs and thighs of chickens and turkeys have dark meat, while the breast has white meat.
INTERNET RESOURCES:
** Penn State University - Embryology in the Classroom
** Purdue University - Avian Classroom
** University of Illinois Extension - What Is a Chicken?
** University of Illinois Extension - Combs
** University of Illinois - Chicken Feet
** University of Illinois - Chicken Feathers TEST:
1. Which of the following statements correctly defines anatomy?
2. Which of the following serves as the cooling system of a chicken?
3. Which better describes the feathers of females?
4. List three of the features that are often used to identify breeds and varieties of chickens.
5. Which of the following is used as part of the respiratory system of a chicken?
6. Trace the route that chicken feed follows as it is eaten and digested by a chicken. Put the following words in order from the beginning to the end of the digestion process: beak, crop, esophagus, gizzard, proventriculus, small intestine, ventriculus. 7. An organ of a chicken that is similar to a stomach is called the __________ . 8. An avian is a cold-blooded vertebrate. TRUE or FALSE?
9. Which of the following is used for insulation?
10. Which bird will have the highest respiration rate?
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PT103 Basic Avian Anatomy and BiologyTEACHER'S GUIDEOBJECTIVE: Students will be able to describe and discuss the management significance of anatomical features and biological processes of avian species used in the poultry industry to produce eggs and poultry meat. PREPARATION: Review lesson content and be prepared to discuss exercise questions with your students. You may want to review the sites suggested under Internet Resources to determine which would be most appropriate and helpful for your class. INTERNET RESOURCES:
** Penn State University - Embryology in the Classroom
** Purdue University - Avian Classroom
** University of Illinois Extension - What Is a Chicken?
** University of Illinois Extension - Combs
** University of Illinois - Chicken Feet
** University of Illinois - Chicken Feathers IMPORTANT TERMS: anatomy, biology, combs, crop, enzymes, esophagus, gallus, Gallus domesticus, heart, life processes, medullary bone, myoglobin, proventriculus, rectum, respiration, social order, wattles. EXTENSION: Offer extra credit for students, or a team of students who use their computer research skills to find and prepare an organized set of illustrations showing anatomical features of chickens and/or other avian species used in poultry production. These illustrations could be printed or loaded into computer files and made available to other class members interested in avian anatomy. EXERCISE ANSWERS: 1. Answers will depend on students' interests and the amount of scientific detail individuals find of interest. Some sites include scientific discussions, while others provide more basic educational information. Some have useful illustrations that some students may find interesting and informative. 2. Answers will depend on the imagination and creativity of students. A few examples:
3. Leg muscles need to be stronger than breast muscles. Leg and thigh muscles are used to move around, to walk, run and jump. That is why leg and thigh muscles need more red fibers that receive a larger blood flow with more oxygen-carrying myoglobin. This oxygen is used for aerobic metabolism, which is the process of producing energy by burning carbohydrates and fats. TEST KEY:
1. Which of the following statements correctly defines anatomy? Correct answer: A. The study of the parts and structures of an animal
2. Which of the following serves as the cooling system of a chicken? Correct answer: A. Comb
3. Which better describes the feathers of females? Correct answer: B. They have rounded ends 4. List three of the features that are often used to identify breeds and varieties of chickens. The lesson listed the following:
5. Which of the following is used as part of the respiratory system of a chicken? Correct answer: C. Skeleton
6. Trace the route that chicken feed follows as it is eaten and digested by a chicken. Put the following words in order from the beginning to the end of the digestion process: beak, crop, esophagus, gizzard, proventriculus, small intestine, ventriculus. 7. An organ of a chicken that is similar to a stomach is called the proventriculus. 8. An avian is a cold-blooded vertebrate. TRUE or FALSE? FALSE. An avian is warm-blooded.
9. Which of the following is used for insulation? Correct answer: B. Feathers
10. Which bird will have the highest respiration rate? Correct answer: B. A very small bird CROSSWORD PUZZLE ANSWERS:
Across: 3. Comb, 5. Crop, 7. Wattles, 9. Females, 11. Down, 12. Gallus, 13. Teeth, 14. Beak, 15. Medullary, 16. Molting. END
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