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CHICK EMBRYOLOGY WHAT ARE THE PROPER TERMS USED IN DESCRIBING POULTRY? Poultry is the group name for all domesticated birds used for meat, eggs, or feathers. A baby chicken of either sex is a chick. A young male chicken is a cockerel. A castrated (neutered) male chicken is a capon. A mature male chicken is a rooster. A young female chicken is a pullet. A mature female chicken is a hen. A group of chickens is a flock. WHAT ARE THE PROPER TERMS USED IN DESCRIBING POULTRY? A. Chickens are classified as layers or broilers. Layers are chickens used to produce large quantities of eggs. On average layer hens produce 250 to 270 eggs per year. Broilers are six- to seven-week-old chickens weighing about 4 pounds that are used for meat because they are tender. WHAT ARE THE DIFFERENT, BREEDS, AND VARIETIES OF CHICKENS? We have two breeds of chicken in our incubator: 1. The White Leghorn. The Leghorn is the most popular layer breed in the United States. This breed is also known for its ability to take flight. Leghorns produce white eggs. They express yellow skin, yellow shanks, white earlobes, and reddish-bay eyes. They are somewhat smaller than most breeds, and tend to be noisy. The chicks are white in color. WHAT ARE THE DIFFERENT, BREEDS, AND VARIETIES OF CHICKENS? 2. Rhode Island Red The Rhode Island Red is a dual-purpose breed; that is, it is raised for meat and eggs. The breed is dark red and lays brown eggs. Rhode Island Reds have yellow skin, yellow shanks, red earlobes, and reddish-bay eyes. Chicks are a light red to tan color with two dark brown bars running down their backs. HOW DOES THE PROCESS OF FERTILIZATION TAKE PLACE IN A CHICKEN EGG? The yolk is released into the oviduct (a long, spiraling tube in the hen's reproductive system), where it can be fertilized internally (inside the hen) by a sperm. Fertilization of a chicken egg takes place when the sperm unites with the egg, forming the blastoderm. Unfertilized eggs will go through the same process however, it will form a blastodisc. A blastodisc will not be a dark white Not symmetrically round Can an un-fertilized egg develop an embryo? CAN AN UNFERTILIZED EGG ACTUALLY DEVELOP? Parthenogenesis is an inherited trait that causes the development of unfertilized eggs. About 1% of parthenogenetic embryos will develop and hatch with deformities. Parthenogenesis is more common in turkeys than in chickens. WHAT ARE THE INTERNAL PARTS OF AN EGG AND WHAT ARE THEIR FUNCTIONS? 1. Blastoderm/blastodisc 2. Yolk: Produced by the hen's ovary in a process called ovulation. It is the yellow, inner part of the egg where the embryo will form. The yolk contains the food that will nourish the embryo as it grows. WHAT ARE THE INTERNAL PARTS OF AN EGG AND WHAT ARE THEIR FUNCTIONS? 3. Vitelline (yolk) membrane - the membrane that surrounds the yolk. 4. Thick albumin - the stringy part of the egg white (albumin) located nearest the yolk. 5. Thin albumin - the watery part of the egg white (albumin) located farthest from the yolk. 6. Chalaza - a spiral, rope-like strand that anchors the yolk in the thick egg white. There are two chalazae anchoring each yolk, one on the top and one on the bottom. WHAT ARE THE INTERNAL PARTS OF AN EGG AND WHAT ARE THEIR FUNCTIONS? 7. Inner shell membrane - the thin membrane located between the outer shell membrane and the albumin. 8. Outer shell membrane - the thin membrane located just inside the shell. 9. Air cell - an empty space located at the large end of the egg; it is between the inner and outer shell membranes. 10. Shell - the hard, protective coating of the egg. It is semi-permeable; it lets gas exchange occur, but keeps other substances from entering the egg. The shell is made of calcium carbonate. Label the Chick Egg WHAT IS THE IDEAL ENVIRONMENT FOR INCUBATING EGGS ARTIFICIALLY? Four Factors must be present for ideal incubation conditions: A. Temperature. Optimum temperature for hatching chickens is between 99 and 100 degrees F. B. Humidity. Eggs lose moisture during development and low humidity causes an increased loss. High humidity can prevent the correct evaporation of water. WHAT IS THE IDEAL ENVIRONMENT FOR INCUBATING EGGS ARTIFICIALLY? C. Ventilation. Proper circulation is critical to assure a fresh supply of oxygen and removal of carbon dioxide. D. Position and turning of eggs. The head of the chick must face the large end of the egg for proper hatching. Eggs should be incubated large end up, and turned three to five times daily to prevent the developing embryo from attaching to the shell membrane. HOW DO WE PREPARE EGGS FOR HATCHING AND CARE FOR YOUNG BIRDS DURING BROODING? Fertility of eggs can be determined by a process known as candling. A. Eggs held up to an egg candler, a device for shining a light beam into an egg. Eggs will look different depending on fertilization or lack of fertilization. Fertile eggs will appear darker as the developing embryo begins to form. Infertile eggs can be detected after 15 to 18 hours of incubation. Between the following poultry species, who has the longest incubation period? Shortest? WHY? - Duck Pigeon Ostrich Chicken Turkey HOW DO WE PREPARE EGGS FOR HATCHING AND CARE FOR YOUNG BIRDS DURING BROODING? Different breeds of poultry have different incubation lengths: Bird: Incubation: Chickens 21 days Ducks/Turkeys 28 days Pigeon 18 days Ostrich 42 days Do not candle or turn the eggs the last three days of incubation. WHAT IS THE PROCESS OF CHICK DEVELOPMENT DURING INCUBATION? Day 3: Day 6 Body parts have begun to for The embryo will have a distinct question mark shape Heart begins to beat Voluntary movement begins formation of reproductive organs and differentiation of sex Day 9 Egg tooth begins to form Body parts can be clearly recognized WHAT IS THE PROCESS OF CHICK DEVELOPMENT DURING INCUBATION? Day 12 Day 16 Beginning of feathers Beak, claws become to harden Embryo continues to grow and moves into position to break the shell Day 20-21 yolk sac completely drawn into body cavity; embryo occupies practically all the space within the egg except the air cell When the air cell is broken, the embryo only has a limited time to pip its way out of the egg. WHAT IS THE PROCESS OF CHICK DEVELOPMENT DURING INCUBATION? http://www.youtube.com/watch?v=tof5b1Qs_OE&feature=related WHAT ARE THE VARIOUS STAGES IN THE EMBRYONIC DEVELOPMENT OF A CHICKEN? A. The blastoderm spreads over the yolk. 1. The blastoderm differentiates into two layers, known as the ectoderm and entoderm, by a process known as gastrulation. 2. The ectoderm, forming first, creates the skin, feathers, beak, claws, nervous system, eye lens and retina, and linings of both mouth and vent. 3. The entoderm, forming second, creates the linings of the digestive tract, as well as the respiratory and secretory organs. 4. A third layer, the mesoderm, finally gives rise to bones, muscles, blood, and reproductive and excretory organs. B. Membranes cover the developing embryo for protection and aid in development. 1. The chorion is a membrane that surrounds the yolk sac and amnion during chick development. 2. A transparent sac, known as the amnion, is full of colorless liquid that surrounds the embryo. The amnion serves as a cushion and provides protection for the developing embryo. 3. The allantois is a sac connected to the abdomen of the developing chick that makes respiration possible it stores excretions, absorbs albumen for food, and gets calcium from the shell for the structural needs of the embryo. WHAT FACTORS WILL AFFECT THE HATCHABILITY OF EGGS? Hatchability refers to the percentage of fertilized eggs that hatch. A. Factors that affect hatchability include: 1. Fertility, the capacity to reproduce, is affected by: a. number of females mated to a single male. b. age of breeding animals. c. length of time between breedings. d. management practices. 2. Genetics, or genetic makeup of the bird, is affected by: a. inbreeding b. crossbreeding c. lethal genes d. heritable traits (ex. egg production) 3. Nutrients, available to the developing chick, are affected by: a. rations fed to breeding hens. b. amount of vitamins and minerals in hen rations. 4. Diseases of breeding stock. 5. Egg Selection. Certain physical characteristics can affect hatchability. a. Size. Extremely large or small eggs do not hatch well. b. Shape. Unnaturally shaped eggs do not hatch well. c. Shell quality. Strong shells hatch better than weak shells. d. Interior quality. Upon candling, better interior quality eggs tend to hatch better. 6. Handling of fertilized eggs. Good management practices include: a. Gathering eggs frequently. b. Clean soiled eggs. c. Sanitizing eggs. d. Hold, or prolong start of incubation, for a minimum amount of time. e. Hold eggs at a temperature of 65 degrees F. f. Keep eggs at a relative humidity of 75 to 80%. g. Position eggs with large end up. h. Turn eggs if they are held for more than 7 days. C. In commercial hatcheries, two separate incubators are used for hatching. 1. Incubation of the chick from day 1 through day 19 is done in an incubator known as the setter. The setter has the environmental conditions discussed earlier. 2. Days 19 through 21 are usually spent in an incubator known as the hatcher. The hatchers have slightly lower temperatures (98 degrees) and have chick holding trays that cut down on the debris from hatching eggs that may cause disturbances to other eggs. 3. Incubation times depend on the species of bird being hatched. HOW DO WE PREPARE EGGS FOR HATCHING AND CARE FOR YOUNG BIRDS DURING BROODING? D. Brooding refers to the care of young poultry from the time of hatching through eight to ten weeks of age. Chicks should be removed from the incubator when they have dried and the down becomes fluffed. This drying normally takes about 12 hours. 1. Certain environmental conditions are needed for proper brooding. a. Temperature—When chicks are one day old, the temperature should be between 90 and 95 degrees F. The temperature is generally lowered five degrees per week until a temperature of 70 to 75 degrees is reached, or until the chicks are fully feathered. b. Ventilation—Proper ventilation provides fresh oxygen, removes carbon dioxide, carbon monoxide, ammonia, and keeps bedding dry. c. Moisture—50 to 60% relative humidity is recommended for good feathering. d. Space requirements—Each chick needs 7 to 10 inches of space under the brooder. More brooder space may be required during colder weather
