Animal science

1. Animal Reproduction and
Genetics

2. Terminology
• Objective:
– Define terminology related to
reproductive management and
breeding systems including
castration, colustrum, estrus,
gestation, lactation and parturition.

3. Terminology
• Castration
– Removing the testicles of the male
to prevent breeding
• Colustrum
– First milk
• Gestation
– Time an animal is pregnant

4. Terminology
• Estrus
– When a female is receptive to be
bred
• Lactation
– Period of time that milk is secreted
by the mammary glands
• Parturition
– Than act of giving birth

5. Breeding Systems
• Objective
– Discuss crossbreeding, grading-up,
inbreeding, linebreeding, and
purebreeding

6. Breeding Systems
• Pure Breeding
– Registered male and female animals
– Angus X Angus

7. Breeding Systems
• Cross Breeding
– Mating a male and female of
different breeds
– Angus X Charolais = Crossbreed

8. Breeding Systems
• Inbreeding
– Mating closely related animals
– Brother X Sister
– Son X Mother
– Father X Daughter

9. Breeding Systems
• Linebreeding
– Breeding more distant relatives than
inbreeding
– Cousin X Cousin

10. Breeding Systems
• Grading-Up
– Mating purebred male (sires) to
unregistered or corssbred females
(dams)
– Yorkshire bore X
Yorkshire/Hampshire sow
– Hybrid Vigor
• Superior traits from crossbreeding
• Offspring are better than parents

11. The Female Reproductive
System
Objective: Identify the parts
of the female reproductive
system of livestock

12. Female Tract

13. Female Reproductive System
• Ovary - the ovary is comparable to the
male testicle and is the site of gamete
production.
– A bovine animal has 20,000 potential eggs per
ovary, while a human female has 400,000
potential eggs per ovary.
– Ova are fully developed at puberty and are not
continuously produced as in the male.
– All species contain two functional ovaries except
for the hen which has only a left functioning
ovary.

14. Female Reproductive System

15. Female Reproductive System
The ovaries have three major functions:
• Gamete production
• Secrete estrogen (hormone)
• absence of muscle development
• development of mammary glands
• development of reproductive systems and external
genitalia
• fat deposition on hips and stomach (source of
energy)
• triggering of heat
• Form the corpus luteum

16. Female Reproductive System
• Infundibulum - the funnel shaped portion of
the fallopian tube near the ovary that catches
the ovulated egg.
• Fallopian Tubes (or Oviducts) - pair of
small tubes leading from the ovaries to the
horns of the uterus (5 - 6 inches).
– Fertilization occurs in the oviduct.
– Egg travels from ovary to uterine horn in 3 - 4
days.

17. Female Reproductive System

18. Female Reproductive System
• Uterine Horn - The anterior, divided end of
the uterus in the cow, ewe, and mare. Sow
has only 2 horns, no body, woman has no
horns, only body.

19. Female Reproductive System

20. Female Reproductive System
Uterus - Muscular sac connecting fallopian
tubes and cervix
1. Sustains the sperm and aids in its transport
2. Supports embryo and fetus during
gestation
3. Expels fetus at parturition

21. Female Reproductive System
• Cervix
– Area between
the uterus and
vagina
– Normally closed
– Opens at estrus
and parturition
– (2 -3 inches)

22. Female Reproductive System
• Vagina - the female organ of copulation
1. admits penis
2. receives semen (except in sow)
3. passageway for fetus at parturition
• Bladder - storage organ for urine
• Vulva - extended genitalia; opening for both
urinary and genital tracts

23. Female Reproductive System

24. Reproductive Functions (Female)
Steps in the female reproductive
process:
1. Ovulation
— Produce gamete (ova or ovum)
— Release of egg(s)
— Infundibulum pushes the
ovum into the fallopian tube

25. Reproductive Functions (Female)

26. Reproductive Functions (Female)
2. Estrus (heat, estrous period)
– Period of time when a female will accept a
male in copulation
– The female must stand (standing heat)
to be mounted before the reproductive
process can begin

27. Reproductive Functions (Female)
3. Gestation
— Fertilization to parturition
— Develop embryo in uterus
4. Parturition
— Expel fully developed young at birth
5. Lactation
— Milk production

28. Reproductive Functions (Female)

29. Ovulation Rates
Ovulation Rates by Species
Cow- 1 egg per estrus
Ewe- 1 to 3 eggs per estrus
Sow- 10 to 20 eggs per estrus
Mare- 1 egg per estrus
Hen- Approx. 28 eggs per month

30. Reproductive Terminology
Species Act Offspring
Cows calving calf
Ewes lambing lamb
Sows farrowing pig
Hens hatching chick
Mares foaling foal
Goats kidding kid

31. Reproductive Functions (Female)
Gestation and Lactation Periods:
Species Gestation Period Lactation(Milking)
Cow 283 - 285 days beef 180 - 270 days
dairy 305 - 365 days
Ewe 115 - 142 days 60 - 90 - 120 days
Sow 112 - 115 days 21 - 42 days
Mare 330 - 345 days 90 - 150 days
Woman 270 days ? years

32. Reproductive Functions (Female)
Estrous period length by species:
Cow 12 - 18 hours
Ewe 24 - 36 hours
Sow 48 - 72 hours
Mare 90 - 170 hours
Hens & Women none

33. Reproductive Functions of the
Female
Estrous cycle - time from one heat period (or
menstrual cycle) to the next.
Length of estrous cycle by species:
Cow 19 - 21 days
Ewe 16 - 17 days
Sow 19 - 21 days
Mare 21 - 24 days
Woman 28 days
Hen none

34. The Male
Reproductive Tract
Objective: Identify
the parts of the male
reproductive system
of livestock and
poultry

35. Male Reproductive Tract

36. Male Reproductive Tract
• Scrotum - external sac that holds
testicles outside of the body to
keep sperm at 4-5oF cooler than
the body temperature
• Testicles - the primary male
organs of reproduction
• to produce sperm
• to secrete testosterone

37. Male Reproductive Tract
• Epididymis - Long coiled tube that is
a path for sperm
– Provide passageway for sperm out of the
seminiferous tubules
– Storage for sperm
– Fluid secretion to nourish sperm
– Place for sperm maturation

38. Male Reproductive Tract
• Vas Deferens - slender tube from
epididymis to urethra which moves
sperm to the urethra at ejaculation
• Urethra - long tube from bladder to
penis; passageway for urine and
sperm out of the body

39. Male Reproductive Tract
• Penis - male organ of copulation
which conveys semen and urine
out of the body
• Penis retractor muscle - allows
extension and retraction of the
penis; sigmoid flexure extends in
copulation

40. Male Reproductive Tract
Accessory Glands:
• Seminal vesicles- add fructose and citric
acid to nourish the sperm
• Prostate Gland - located at the neck of
the bladder
– cleans the urethra prior to and during
ejaculation
– provides minerals for sperm
– provides the medium for sperm transport
– provides the characteristic odor of semen

41. Male Reproductive Tract
• Cowper’s gland
• Also called the Bulbourethral gland
• Paired organs
• cleans the urethra prior to semen
passage

43. Male Reproductive Tract

44. Reproduction in
Poultry
Objective: Specify how the
reproductive system for
poultry functions

46. Reproduction in Poultry
The poultry oviduct has five parts:
1) Vagina
– Holds the egg until laid
2) Uterus
– Secretes the shell
3) Isthmus
– Adds the two shell membranes
4) Magnum
– Secretes the albumen
5) Infundibulum
– Where fertilization takes place

49. Reproduction in Poultry
• Major difference:
– Embryo of livestock develop inside the
female’s body while the embryo of poultry
develops inside the egg.
• Poultry only have the left ovary and
oviduct when mature
• The yoke is the ovum
• Chicken Incubation
– 21 days

50. Poultry Reproduction
In your notes, define the following
poultry reproductive terms and tell
how they differ from livestock we have
studied so far:
•Papilla
•Testicles
•Cloaca
•Vent
•Ovary
•Magnum
•Isthmus
•Uterus
•Vagina
Follow the
Lecture

51. Assignment:
Build a crossword puzzle
containing 12 reproductive terms
from your class notes. Have
another student complete and
sign your crossword puzzle. The
assignment as well as your other
assignment from the handout is
due at the end of class.

52. Animal Reproduction and
Genetics
Objective: Describe the cell and
process involved in cell division
including how genes affect the
transmission of characteristics

53. Animal Cell
• The body is made up of millions of
tiny cells
• Most of the cell is made up of
protoplasm
• Cell parts:
 Nucleus
 Cytoplasm
 Cell membrane

54. Animal Cell
Nucleus
Cytoplasm
Cell
Membrane

55. Cell Division
• Mitosis
– Increases total number of cells
– Results in animal growth
– Chromosomes pairs are duplicated
• Meiosis
– Produces gametes
– Only have one-half the
chromosomes of normal cells

56. Fertilization
• When the sperm from a male
reaches the egg from a female
• Two cells join to form a
complete cell
• Pairs of chromosomes are
formed again
• Many different combinations of
traits are formed

57. Fertilization

58. Chromosomes
• Rod shaped
bodies
• Made of protein
• Found in the cell
nucleus
• Exist in pairs
except for
gamete cells
• The number of
chromosome
pairs differ for
various animals
– Cattle 30
– Swine 19
– Horses 33
– Chickens 6
– Humans 23

59. Genes
• Located on chromosomes
• Thousands found in each animal
• Control inherited characteristics
– Carcass traits
– Growth rate
– Feed efficiency
• Two types of inherited traits
 Dominant
 Recessive

60. Assignment
1. Read pages 186
• Livestock and Poultry Production
textbook
2. Complete problems 1-9
3. Write the question and provide a
short answer in complete
sentences.

61. Genes
• Dominant gene
– Hides the effect of another gene
– Polled condition in cattle is dominant
– The gene is represented by a capital
letter
• Recessive
– Gene that is hidden by another
– The gene is represented by a lower
case letter

62. Genes
Example:
The dominant gene is written- P
The recessive gene is written-p
P= Polled
p= horned

63. Homozygous and Heterozygous
• Homozygous gene pair
– Carries two genes for a trait
– Polled cow might carry the gene PP
• Heterozygous
– Carries two different genes that
affect a trait
– Polled cows might carry a recessive
gene with the dominant Pp

64. Predicting Genotype
• Genotype-kind of gene pairs
possessed
• Phenotype- the physical
appearance of an animal
• Punnett squares are used to
predict genotypes and phenotypes
of animals

65. Punnett Square
P= Polled
p= horned
Example:
• Two polled cattle
that are
homozygous for
the polled trait
P P
P PP PP
P PP PP
Polled Dam

66. Punnett Square
N= Normal size
n= Dwarfism
Example:
• Normal size in
cattle is dominant
to dwarfism
N N
N NN NN
n Nn Nn
Normal Dam

67. Punnett Square
N= Normal size
n= Dwarfism
Example:
• What if both
parents are
carriers for a trait
or disorder?
N n
N NN Nn
n Nn nn
Normal Dam
Result: one out of every four births
could result in a dwarf animal (1:2:1)

68. Assignment
Complete a Punnett
Square for two
animals that are
heterozygous for
two traits:
• Polled=P
• Black= B
(Alternatives are horned
and red)
Dam
Sire

69. Answer
A Punnett Square
for two animals
that are
heterozygous for
two traits:
• Polled=P
• Black= B
(Alternatives are horned
and red)
PB Pb pB pb
PB PPBB PPBb PpBB PpBb
Pb PPBb PPbb PpBb Ppbb
pB PpBB PpBb ppBB ppBb
pb PpBb Ppbb ppBb ppbb
Dam
Sire
9:3:3:1

70. Heritability
• Objective:
– Discuss hertability estimates for beef
and swine

71. Heritability
• Estimated the likelihood of a trait
being passes on from the parent
to the offspring
– Low heritability
• slow herd improvement
– High heritability
• faster improvement

72. Heritability
• Swine rates are usually lower than
cattle
• Heritiability for carcass traits are
higher than reproductive traits
• Estimates vary from 0 to 70%

73. Birth weight 40%
Weaning Weight 25-30%
Yearling Weight 60%
Fertility 10%
Tenderness 60%

74. Heritability Review
• Herd improvement
– slow for low heritability
– faster for high heritability
• Estimates are higher for:
– beef compared to swine
– carcass traits compared to repro