1. Unit B Understanding Animal Body Systems
Lesson 7
Understanding Animal Reproduction

2. Terms Anestrus Estrus Artificial insemination Fertilization Gestation
Castration
Cervix
Copulation
Diestrus
Egg
Ejaculation
Estrous cycle
Estrus
Fertilization
Gestation
Heat
Insemination
Lactation
Metestrus
Natural insemination
Neutering

3. Terms
Ovary
Oviduct
Parturition
Penis
Proestrus
Prostate gland
Puberty

4. Why is reproduction important?
Reproduction is the process by which animals produce offspring.
Offspring are the same species and have traits of their parents.
Parents are selected and mated to achieve certain goals with offspring.

5. Goals of Reproduction
Examples of goals include to produce offspring with high milk productivity or meaty carcasses.
Reproduction results in new animals that are raised for the products they produce.
Examples of products include meat, eggs, milk, and wool.

6. Animal Reproduction
Most animals are produced with sexual reproduction.
Sexual reproduction is the union of a sperm and an egg.
Two parents are required.
Sperm is the sex cell of male animals.
They are produced in the testes.
The egg or ovum is the sex cell of female animals.
They are produced in the ovaries.

7. Animal Reproduction
Fertilization is the process by which the union of a sperm and an egg occurs.
It is also known as conception.
The union of the sperm with the egg occurs in the reproductive tract of the female.
The process of placing sperm in the reproductive tract of the female is known as insemination.

8. Animal Reproduction
Natural insemination occurs when a male of a species mates with a female of the same species.
Sperm are placed in the female reproductive tract by the male during copulation.
Copulation is the mating process in which sperm are ejaculated from the penis of the male in the vagina of the female.
Females must be receptive to males at a time in the estrus cycle known as heat.

9. Animal Reproduction
Artificial insemination is used in some situations, such as with dairy cows.
Artificial insemination is placing semen collected from a male in the female reproductive tract using equipment designed for the purpose.
Artificial insemination must be done when the female is in heat.

10. Animal Reproduction
Once an egg has been fertilized, it becomes an embryo that attaches itself to the uterus for nourishment.
The female is pregnant.
The embryo goes through a time of development and becomes a fetus.
The fetus develops to a stage where it is born and can live outside the uterus.

11. Sexual Classifications
Sexual classification is the condition of an animal based on its age and sexual condition.
It includes animals that are capable of reproduction as well as those that are not capable of reproduction.

12. Sexual Classifications
An animal can be made incapable of reproduction by removing the ovaries or testes or altering the condition of the reproductive organs so that they are no longer fertile.
The animals are not capable of conception.

13. Animals incapable of reproduction
Castration is the process of removing the testes from a male.
It is a management practice used on young male animals.
Castration eliminates unwanted breeding.
It also promotes growth and development of young animals in more desirable ways with food animal production.
Castration may be done surgically or with other methods.

14. Animals incapable of reproduction
Neutering is the process of making a female incapable of reproduction.
It is also known as spaying.
The ovaries of the female are removed or other procedures are used to render the female incapable of conception.

15. Sexual Classifications
A number of terms are used to describe the sexual classification of animals.
These terms vary by species, age, and gender.
For example, a steer is a male bovine castrated at a young age and before sexual maturity was reached.
Textbooks and references usually have lists of terms for the sexual classification of common species.

16. Species
Young
Mature Male
Mature Female
Castrated Male
Cattle
Calf
Bull
Cow
Steer
Sheep
Lamb
Ram
Ewe
Wether
Goat
Kid
Buck
Doe
Chicken
Chick
Rooster
Hen
Capon
Horse
Foal
Stallion
Mare
Gelding
Female – Filly
Male - Colt

17. What are some of the common breeding systems used in livestock production?
Straightbreeding is mating animals of the same breed. There are several variations of this system. Some of the most common are:
Purebred Breeding — A purebred is an animal of a breed in which both parents of the animal must have been purebred.
Inbreeding is the mating of related animals. This increases the genetic purity of the stock produced.

18. Inbreeding Types
Closebreeding is the most intensive form of inbreeding, in which the animals being mated are very closely related and can be traced back to more than one common ancestor.

19. Inbreeding Types
Linebreeding refers to mating animals that are more distantly related and can be traced back to one common ancestor.

20. Grading Up
Grading up is the mating of purebred sires to grade females.
A grade animal is any animal not eligible for registry as a purebred.
This is done as less expensive way to improve the quality of animals on a farm or ranch.

21. Crossbreeding
Crossbreeding is the mating of two animals from different breeds.
The resulting offspring is a hybrid. This generally results in improved traits in the offspring.
Superior traits that result from crossbreeding are called hybrid vigor or heterosis.

22. Estrous Cycle
The estrous cycle is the phases in the reproductive cycle between periods of estrus.
These are the phases of reproductive readiness in the reproductive system of a mature female.
The cycle does not occur during pregnancy nor when a female is in anestrus.
Anestrus is the absence of cycling. It may occur due to disease, not being of reproductive age, or other conditions.

23. Estrous Cycle The estrous cycle is comprised of four phases.
The phases occur in a definite sequence unless the female is pregnant.

24. Phases of the Estrous Cycle
Estrus is the phase when a female is in heat.
The animal is receptive to mating and will stand for copulation with a male.
Females exhibit signs of heat.
An enlarged vulva and a discharge from it are signs.
Some females exhibit behaviors indicating readiness for mating such as when a cow mounts another cow in the mating position.

25. Phases of the Estrous Cycle
Metestrus is the phase following heat.
Ovulation occurs during metestrus as do other processes that help maintain a pregnancy should conception occur.

26. Phases of the Estrous Cycle
Diestrus is the phase in the estrous cycle when the reproductive system assumes that conception has occurred, even if it has not.
Diestrus is several days long depending on the species of animal.

27. Phases of the Estrous Cycle
Proestrus is the period following diestrus in which preparation is being made by the reproductive system for the next heat period and ovulation.
If conception has occurred, the estrous cycle ceases until it is renewed after gestation and parturition.

28. Phases of the Estrous Cycle
Animal producers can be more efficient in animal reproductive management if they know the phases of estrous.
Careful observation by a trained producer and records on reproductive cycles will promote breeding to assure the production of young animals at the best time.
For example, cattle producers often breed cows to assure calving in the spring when pasture grasses are beginning to grow.
This allows a cow to produce maximum milk for the nutrition and growth of the calf.

29. Reproductive Development of Animals
Animals of a species begin life as either a male or female.
Their development as a member of their species includes reproductive development for their gender.
Reproductive development follows fairly definite stages and processes.

30. Reproductive Development of Animals
Prepuberty is the stage of life of a young animal before it is capable of reproduction.
Sufficient development has not been reached for an animal to reproduce.

31. Reproductive Development of Animals
Puberty is the stage when an animal reaches a level of sexual development where it is capable of reproduction.
Puberty occurs in both males and females.

32. Puberty
With females, the estrous cycle results in the release of mature eggs that can support the mating, conception, and gestation processes.
With males, the animal is capable of producing viable sperm.
Age of puberty varies with animal species and other conditions such as nutrition and health condition.
Examples of when puberty is reached are: cattle 8-12 months, sheep 5-7 months, and horses months.

33. Gestation Gestation is the period when a female is pregnant.
The length of gestation varies with species though it tends to be consistent among members of the same species.
For example, the gestation period is 155 days for ewes and 337 days for a mare.
The animal gives birth at the end of gestation.

34. Parturition Parturition is the process of giving birth.
Hormones are produced to support the birth process and prepare for lactation.

35. Lactation
Lactation is the secretion of milk by the mammary glands of a female.
It is initiated by hormone activity.
Lactation lasts for several months following parturition.

36. Mating Behavior Mating behavior is a part of reproductive development.
Both males and females of a species exhibit mating behavior.
With males, this includes libido (desire to mate) and social status within a herd.
With females, receptivity to mating occurs during heat.

37. Summary 1. What is the importance of animal reproduction?
2. List the sexual classification of animals for major species.
3. What are the different breeding programs used in your area?
4. Describe the phases of the estrous cycle
5. How does reproductive development of animals occur?