1. Animal, Plant & Soil Science
Lesson C4-5
Lactation

2. Objectives
Identify the role of natural and synthetic hormones in today’s U.S. milk production.
Examine how factors such as genetics, disease, feed, environment, and body condition affect milk production.

3. Terms alveoli bovine somatotropin colostrum gland cistern ketosis
lactation
lumen
mammary system
mastitis
milk fever
oxytocin
prolactin
sphincter muscle
teats
tertiary ducts

4. What is lactation? What are the necessary components for lactation to occur? What is the function of the mammary glands?
All female animals suitable for reproduction possess the necessary components for lactation to occur.
This allows the mother to supply nutrition to the infant offspring through milk production.
The first milk from a new mother is crucial to the survivability of all newborn animals.
Milk production in female animals occurs through interior and exterior female body components.

5. What is lactation?
A. Lactation is the production of milk by the mammary systems of female animals.
It begins at the same time or shortly after a female gives birth.
Through lactation, a mother releases highly nutritious milk that contains all the key elements needed to support the life of infants.
Lactation is supported by the female consuming nutrients from feedstuffs and water.

6. What is lactation? What are the necessary components for lactation to occur? What is the function of the mammary glands?
The items consumed are converted within the body and released through the mammary system.
The offspring suckles the mammary system, which stimulates the female to release her milk and allows the infant to consume the product.
Milk supports the young animal until it is able to consume other feedstuffs, such as grain or grass.

7. What is lactation? What are the necessary components for lactation to occur? What is the function of the mammary glands?
B. The mammary system contains the components necessary for a female to produce milk.
In the mammary system, the milk manufacturing process begins by blood flowing through specific parts of the system, charging the glands with nutrients and water that are processed and converted to milk.

8. What is lactation? What are the necessary components for lactation to occur? What is the function of the mammary glands?

10. What is lactation? What are the necessary components for lactation to occur?
1. Blood directed toward the mammary system flows through a cluster of grape-like structures called alveoli.
Alveoli extract raw materials from the blood stream and convert the product into milk.
As milk is produced, solids (e.g., proteins, carbohydrates, vitamins, and minerals) are blended with water in the alveoli and released to the next component of the mammary system.

11. What is lactation? What are the necessary components for lactation to occur? What is the function of the mammary glands?
2. Milk secreted by the alveoli flows into a hollow-like cavity called the lumen.
The lumen links a cluster of alveoli together to create a lobule.
Many alveoli are linked by a lumen to create a pathway for the milk to be released from the female body.
Milk is not stored in the lumen; instead, milk flows to the next component of the mammary system.

12. What is lactation? What are the necessary components for lactation to occur? What is the function of the mammary glands?
3. Milk exits the lumen through a specialized structure called the tertiary ducts.
Tertiary ducts provide the pathway from the lumen to the storage compartment of the mammary system.
The gland cistern is where milk remains until it is released from the body.
The size and shape of the gland cistern varies according to animal type, but it typically contains an upper area and lower area where the milk is eventually released.
To keep the milk in the storage compartment, a specialized muscle called the sphincter muscle contracts until milk letdown occurs.

13. What is the function of the mammary glands?
4. Once milk letdown is stimulated through specialized hormones from the female, the milk is released and flows down from the alveoli.
The letdown process utilizes gravity and pressure from additional milk being produced to exit the body through teats.
Teats are elongated exterior structures that contain a small canal at the tip that opens to release milk when suckled or stimulated.

14. What are the components of milk and colostrum?
The manufacturing of milk uses the raw materials consumed by the female through feedstuffs and water.
The materials are broken into individual components in the digestive system and are circulated to the mammary system through the blood stream.
Once the nutritional-rich blood reaches the mammary system, specific nutrients and other components are extracted from the blood and converted to milk.

15. What are the components of milk and colostrum?
The nutrients and components extracted from the blood produce a product that is a highly nutritious source of food, which can support the life of young animals.
The first milk produced by a mother also contains specialized antibodies that protect infants early in life.

16. What are the components of milk and colostrum?
A. Milk supplies the offspring with energy and nutrients needed for survival.
The exact makeup of milk varies by animal, but it is typically composed of approximately 87 percent water and 13 percent solids.
The water serves as the carrying agent for the solids and meets the hydration needs of young animals.
Early in life, infants cannot physically consume water or have not developed the instincts to facilitate consumption at a level that would prevent dehydration.
Without consuming milk to supply water to young animals, death would occur quickly.

17. What are the components of milk and colostrum?
B. The solids in milk are composed of protein, carbohydrates, water-soluble vitamins, and minerals.
The levels of each component vary by animal due to the environment they live in and feedstuffs the mother consumes.
For example, some animals produce milk with higher levels of carbohydrates because the offspring require higher levels of energy to survive in that particular environment.

18. What are the components of milk and colostrum?
Other animals may produce milk with higher levels of protein to support rapid growth and development of young animals.
Milk is commonly consumed by humans as part of their daily diet and supplies calcium and Vitamin D to support healthy living and a balanced diet.

19. What are the components of milk and colostrum?
C. The first milk produced by a mother is called colostrum.
Colostrum contains high levels of antibodies that are passed to newborns to aid in survivability.
It provides the antibodies that develop into the immune system and fight off disease or sickness.
Without colostrum, a young animal will likely perish in the first few days of life.
The antibodies in colostrum originate from the immune system of the mother.

20. What are the components of milk and colostrum?
A level of resistance to disease and sickness is released from the mother’s immune system and is directed to the mammary system through the blood stream.
Once milk production is stimulated at birth, the antibodies are included in the first milk produced.
High enough levels of antibodies remain in the mammary system and are included in the milk for the first few days of milk production.
Eventually the antibodies are used up, and colostrum is no longer produced.

21. How do natural and synthetic hormones influence milk production in the United States?
Naturally produced and synthetic hormones are utilized in milk production.
They are primarily utilized to increase milk production, to enhance animal well-being, and to improve reproduction.
Without taking these factors into consideration, milk production would be well below its current levels.

22. How do natural and synthetic hormones influence milk production in the United States?
The naturally produced hormones may be limited or void due to a health condition, allowing for dairy producers to supplement synthetic hormones to meet production needs.
Before a synthetic hormone is used in animals, it must be approved as safe by the U.S. Food and Drug Administration.

23. How do natural and synthetic hormones influence milk production in the United States?
A. Many hormones occur naturally in an animal’s body to influence milk production.
These hormones serve as triggers to begin milk production, stimulate milk letdown, and start the reproductive process over again.

24. 1. Lactation begins around the time of offspring birth
1. Lactation begins around the time of offspring birth. It is triggered by a hormone called prolactin, which is a naturally produced hormone that is released to trigger the mammary glands to begin milk production.
It is produced throughout the pregnancy process and peaks shortly before giving birth.
The peak in prolactin triggers the mammary glands

25. How do natural and synthetic hormones influence milk production in the United States?
2. Once lactation begins and the mammary system begins producing milk, the mammary system must be triggered to release the milk.
The hormone oxytocin has this role.
Oxytocin is a naturally produced hormone that is released to start the milk-releasing process from the mammary system.
The release of oxytocin is stimulated by the suckling of an infant animal or cleaning of the teats in dairy animals.
It also serves other roles in the body of female animals, such as stimulating the birth process once the fetus has reached maturity.

26. How do natural and synthetic hormones influence milk production in the United States?
3. Milk production cannot occur without first giving birth to offspring.
Therefore, the reproductive cycle should be considered when evaluating the influence of naturally produced hormones on milk production.
Some animals produce hormones that prevent becoming pregnant while lactating; others can become pregnant again within a few days to a few months of giving birth.

27. How do natural and synthetic hormones influence milk production in the United States?
For example, horses can rebreed within a few days of giving birth, while cows need a few months before they can become pregnant again.
Whether an animal can become pregnant again or not is determined by naturally produced hormones.
In some animals, rebreeding is possible once lactation ceases.
These animals begin the lactation process again after giving birth.

28. How do natural and synthetic hormones influence milk production in the United States?
B. Many of the naturally produced hormones discussed previously are also produced in a synthetic form.
However, researchers began trying to produce synthetic hormones in the 1920s to increase milk production.
The goal was to create a synthetic hormone for commercial use that would safely enhance animal milk production.

29. How do natural and synthetic hormones influence milk production in the United States?
In the mid-1990s, a synthetic form of bovine somatotropin (bST) was released for use in dairy cows.
Bovine somatotropin is a naturally released hormone that regulates milk production levels.
When supplemented in a synthetic form, cows produce more milk for a longer period of time than untreated cows.

30. How do natural and synthetic hormones influence milk production in the United States?
1. Cows treated with a synthetic form of bST experience an increase in milk production early in the lactation period.
Naturally, cows produce more milk for the first several weeks after giving birth and begin to taper off over several months.
When a synthetic form of bST is administered, cows continue to produce a high level of milk for a longer period of time.

31. How do natural and synthetic hormones influence milk production in the United States?
A specifically designed schedule is created for each cow to determine when she will be injected with bST and for what time frame.
The increased milk production allows dairy producers to better utilize the output of each cow and to increase sales.

32. How do natural and synthetic hormones influence milk production in the United States?
2. Bovine somatotropin is a naturally produced protein hormone found in animals.
By introducing it in a synthetic form for a period of time, cows produce more milk for a longer period of time.
It is manufactured using a similar process utilized to create hormones for medical use in humans and animals.
The gene cells that produce bST naturally are extracted from a cow’s pituitary gland and combined with other cells that stimulate growth.

33. How do natural and synthetic hormones influence milk production in the United States?
The bST cells are spliced into the growth cells to create a large batch of product.
Then these cells are fermented to grow and develop into a form of bST.
The new synthetic bST cells are purified and enhanced into the synthetic form before being available for the treatment of cows.

35. Review
What is lactation? What are the necessary components for lactation to occur? What is the function of the mammary glands?
What are the components of milk and colostrum?

36. Review
How do natural and synthetic hormones influence milk production in the United States?
How do factors such as genetics, disease, feed, environment, and body condition affect milk production?