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The effects of hormones, estrogen and testosterone on the secondary sex characteristics of white leghorn chickens.
Mar Sanchez
CP Biology 7th Period
Senkler
5/9/08
I. Purpose
The purpose of this lab is to see how male and female White Leghorn
Chickens and their secondary sex characteristics are affected by the testosterone and estrogen injected into the flow of the endocrine system.
II. Background
The following research discloses the characteristics of white leghorn chickens, secondary sex characteristics of each sex, the glands and hormones involved in producing these sex characteristics, and how control systems affect the results of each injection of a steroid hormone.
In White Leghorn chickens, they have the ability of greater flight than most other chickens. Many have been known to build their nests within the safety of tree branches. Most of this species are relatively small and range from about six pounds for males to about four point five pounds for hens. There is a large variety in the characteristics of the chickens. For example, single and rose comb chickens in a variety of brown, white, buff, black, silver, red, black tailed red,
and Columbian. These chickens have a tendency to be good foragers and noisy. The White Leghorn Chicken is the best species of chicken for egg laying in America. Breeding stock in chickens can ensure such qualities in offspring as large egg, better shell, and a good interior of the egg. The chickens mature quickly and are often used in lab work. The species itself is said to have originated from Leghorn, Italy. Most tend to have a yellow skin color and lay white shelled eggs.
A male chicken is a cock or a cockerel, depending on its age. Similarly, a female chicken is called a pullet or a hen. A chicken is a cockerel or pullet if it is less than one year of age. After one year of age, the chicken is referred to as a hen or cock. In the commercial chicken industry a female chicken is called a hen after it begins egg production around five months of age. A sexually mature male chicken, around five months of age, is referred to as a rooster. Typical differences between a rooster (Figure 1) and a hen (Figure 2) include:
a. The male has a larger body, comb, and wattles than the female.
b. In single-comb birds the male's comb will be turgid and stand erect, whereas the females may flop over on one side.
c. The male has a larger, more developed spur than does the female.
d. Roosters crow, while hens do not.
e. In multicolored varieties, the male will have more variety of colorings in his plumage than the female.
f. The male has longer and more pointed hackle feathers than the female.
The male and female both have main tail feathers, but only the male has saddle feathers
The best method to determine sex is by observing the chicks' behavior. Startle the chicks by sailing a hat or similar soft object over their heads and watch their reactions. The cockerels will instinctively stand erect with their heads upright and will emit a peculiar warning chirruping sound. The pullets will tend to crouch down low and remain silent. The following table shows the most common differences in development between the sexes of heavy breed chicks at 5 week of age.
Cockerel 5 Weeks of Age Pullet
Medium size, pinkish Comb Small, yellowish
Sturdy, long Legs Finer, shorter
Stumpy, curved Tail Longer, straight
Downy with thin line of stub feathers down centre Back More advanced feathering along centre & flanks
Feathering poorly advanced Side of neck, crop & flanks Feathering well advanced
Bare, showing wing covert quills Wing bows Covered with small feathers
Erect and alert Carriage Lower set
There are two glands and hormones involved in producing sex characteristics in chicken. The one major hormone in female chickens is that of estrogen. Estrogen comes from the ovaries and controls reproductive behavior, regulates the endocrine system, and assists in the characteristics of the female chicken’s body (such as comb). A major hormone is male and female chickens are testosterones. Testosterone is secreted in the testis of males, and ovaries in females. Testosterone plays a key role in health and well-being as well as in sexual functioning. Examples include enhanced libido, increased energy, increased production of red blood cells and protection against osteoporosis.
The expected effects on the cockerels and pullets after an injection of either hormone differ from each other. If a cockerel is injected with estrogen, it is expected that a decrease in comb length and height, and the gaining of weight would occur. Also it would become less active, and talkative. If a cockerel is injected with testosterone, it is expected that the normal growth rate of its comb length and height will continue. When a pullet is injected with estrogen, its normal comb length, and height growth would occur. If a pullet is injected with testosterone the chick would become much more active, and talkative. Also the pullet would expect an increase in height, comb index, and weight.
Although those may be the expected effects, different factors, such as
control systems may affect the results. Examples of these systems include negative feedback, the hypothalamus, and the pituitary glands. Negative feedback, which is the process where response diminishes original stimulus, could affect the process by dropping the blood-calcium level therefore stopping secretion. The hypothalamus and the pituitary gland could affect the process by secreting other hormones to balance out—or in other words “maintain homeostasis.”
This research provided information the characteristics of white leghorn chickens, secondary sex characteristics of each sex, the glands and hormones involved in producing these sex characteristics, and how control systems affect the results of each injection of a steroid hormone.
III. Hypothesis
A. Variables
This experiment consisted of three different variables, the control, independent, and dependent variables. The control Variable, which is the standard in to compare the dependent and independent variables to, was the saline injection. The independent variables to be tested were low and high testosterone, and estrogen injections. The dependent variable data’s to be measured were the changes in mass and comb index.
B. Pre-lab Prediction
1. Chickens injected with estrogen will have smaller changes in comb index compared to chickens injected with saline because when the estrogen is injected into the chick, the hormone naturally decreases the growth of comb index, height, and mass.
2. Chickens injected with testosterone will have larger changes in comb index compared to chickens with saline because when the testosterone is injected into the chick, the hormone naturally increases the growth of comb index, height, and mass.
IV. Procedure
Materials List:
6 cages
Chicken feed
Water
5 sterilized needles
Low dose of Estrogen
High dose of estrogen
Low dose of Testosterone
High dose of Testosterone
Saline solution
Basic hand soap
4 Scales (grams)
Metric Ruler
Lab Notebook
150 White Leghorn chicks (half male and half female)
Lab room
Three different colored markers
Different colored numbered leg bands
Newspaper
Bleach in spray bottle
Writing utensil
150 students
Step by step Procedure:
Separation into experimental groups and chicken identification:
1. Assign an equal amount of chicks of both A and B (male and female) variety to
the five different injection groups.
2. Take the assigned chick from the cage with its gender specific peers and place
and record a numbered and colored band on one of its legs.
3. Mark its back with an assigned color marker between the head and the tail
feathers. It is extremely important that marks stay in this located space as to the full
safety of the chicks.
4. Record the chick’s band number and symbol down both in the lab notebook each
student has to enter information in about their chick, and the teachers designated list.
5. Place the student’s specific chicken within the numbered cage of the injection
group previously assigned to each student and NOT that of the gender group.
Care of Chickens:
1. Twice a day pull out the bottom of the cage and roll up the old used news paper and
throw into garbage.
2. Place the new double layer of newspaper into the bottom of the cage then slide the
tray back into the cage.
3. Sweep all floors and counters free of rubbish and clean tables of any feces the chicks
may have left behind.
4. Verify that chicks have an adequate amount of food and water. If not supply the
adequate amounts of food and water.
5. Proceed in bleaching all counters everyday the chicks are out of cages for either data
collection or injections.
2. Finish everyday that chickens have been handled with hand washing.
Data Collection:
1. After removing the chicken from the designated injection cage begin weighing
the mass of chickens in one of the four scales record the data in the lab notebook.
2. Measure with the metric ruler the comb length from the start of the comb on the
chicks forehead to the bottom of the chicks forehead. Record this data in millimeters
within the lab notebook.
3. Measure the width of the chicks comb from one side of the comb to the other.
Record this data in the lab notebook in millimeters.
4. Measure from the skin of the chickens head to the top of the chickens comb the
comb height. Again, record this data within the lab notebook using millimeters.
5. Place chicks with other chicks that vary in cage type as well as gender.
6. Observe and record the way all of the chickens interact with each other as well
as the personality traits displayed by each chicken. Record this data within the lab
notebook.
7. Multiply the comb height, width, and length and record inside the lab notebook.
8. Repeat steps 1- 6 on all measurement days within the lab.
Injection:
1. On all of the three injection days remove chick from their injection specified cages
and receive the correct amount of the numbered injection solution.
3. Hold the chicken on its back and restrain the head.
4. Locate the blue vain on its neck that is above the wing.
5. Hold the chicken steady and inject below the chickens skin with the needle pointed
down.
6. Return chicks safely inside cages
VI. Discussion:
The outcome of the chicken lab was interesting in that it displayed the hypothesis that was previously stated. Each gender and each injection group underwent a period of time in which they gained mass as well as length, height, and width of the comb. Therefore, it was these outcomes that gave proof in deducing the gender and hormone groups of chicks.
The results shown on Table 5: Average Change in Mass and Comb Index compare the measurements of the mass and comb index differences between the A and the B group. The determining factor to base the decision on is the change in mass between groups A and B. Based on the expected sex characteristic differences, test group A chickens are females and test group B chickens are males. Looking at Table 4: Class Chicken Data, test group 1A had an average change in mass of 98.06 grams compared to test group 1B change in mass of 89.29 grams. Test group 2A had an average change in mass of 125.08 grams compared to test group 2B change in mass of 99.09 grams. Test group 3A had an average change in mass of 131.26 grams compared to test group 3B change in mass of 108.59 grams. Test group 4A had an average change in mass of 116.09 grams compared to test group 4B change in mass of 89.72 grams. Lastly, test group 5A had an average change in mass of 116.41 grams compared to 5B change in mass of 101.91 grams. In each test group the female chickens had a larger change in mass than the male chickens. The expected sex differences in chickens is that the females will have a larger change in mass due to...
The results of shown in Graph 2: Average Change in Comb Index Comparing all 10 Groups compares the comb index and its differences between the five different test groups. The determining factor to base the decision on is the change in comb index between test groups 1, 2, 3, 4, and 5. Based on the expected effects of hormone differences injection 1 is high testosterone, injection 2 is high estrogen, injection 3 is saline solution, injection 4 is low testosterone, and injection 5 is low estrogen. Looking at Table 5: Average Change in Mass and Comb Index test group 1 had an average change in comb index of 2165.77 mm for A's and 2620.2 mm for B's. Test group 2 had an average change in comb index of 654.83 mm for A's and 319.54 mm for B's. Test group 3 had an average comb index of 627.55 mm for A's and 349.33 mm for B's. Test group 4 had an average comb index of 2328.82 mm for A's and 2867 mm for B's. Test group 5 had an average change in comb index of 569.92 mm for A's and 719.8 mm for B's.
- The expected effects that testosterone
+ The expected effects that testosterone produces is larger changes in comb indexes. The two groups that had the largest change in comb index were injection 1 and injection 4. These are the two testosterone test groups. To determine which of these groups was high dose of testosterone vs. low dose of testosterone the negative feedback control system was considered. The negative feedback system will trigger the stopping of testosterone secreation. It is the testosterone in the body of the chick that results in a larger comb index. This is why the high dose group which had more testosterone had a smaller comb index than that of the small testosterone dose group.
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