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Animal Reproduction and
Genetics
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ANIMALSCIENCE
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Terminology
• Objective:
– Define terminology related to reproductive
management and breeding systems including
castration, colustrum, estrus, gestation,
lactation and parturition.
WF-R ANIMAL SCIENCE 1
Terminology
• Castration
– Removing the testicles of the male to
prevent breeding
• Colostrum
– First milk produced after a mammal gives
birth that contains antibodies needed for
immunity.
• Gestation
– Time an animal is pregnant
WF-R ANIMAL SCIENCE 1
Terminology
• Estrus
– When a female is receptive to be bred (also
called ‘in heat’)
• Lactation
– Period of time that milk is secreted by the
mammary glands
• Parturition
– The act of giving birth
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Breeding Systems
• Objective
– Discuss crossbreeding, grading-up,
inbreeding, linebreeding, and purebreeding
WF-R ANIMAL SCIENCE 1
Breeding Systems
• Pure Breeding
– Registered male and female animals
– Angus X Angus
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Breeding Systems
• Cross Breeding
– Mating a male and female of different breeds
– Angus X Hereford = Crossbreed
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Breeding Systems
– Hybrid Vigor
• Superior traits from crossbreeding
• Offspring are better than parents
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Breeding Systems
• Inbreeding
– Mating closely related animals
– Brother X Sister
– Son X Mother
– Father X Daughter
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Breeding Systems
• Linebreeding
– Breeding more distant relatives than
inbreeding
– Can be traced back to a common ancestor,
such as a grandparent
– Cousin X Cousin
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Breeding Systems
• Grading-Up
– Mating purebred male (sires) to unregistered
or crossbred females (dams) to improve herd
– Yorkshire bore X Yorkshire/Hampshire sow
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The Female Reproductive
System
Objective: Identify the parts of the
female reproductive system of
livestock
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Female Tract
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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.
WF-R ANIMAL SCIENCE 1
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
WF-R ANIMAL SCIENCE 1
Female Reproductive System
• Infundibulum - the funnel shaped portion of the
fallopian tube near the ovary that catches the ovulated
egg.
• 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.
WF-R ANIMAL SCIENCE 1
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
WF-R ANIMAL SCIENCE 1
Female Reproductive System
• Cervix
– Area between the
uterus and vagina
– Normally closed
– Opens at estrus
and parturition
– (2 -3 inches)
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Female Reproductive System
• Vagina - the female organ of copulation
1. admits penis
2. receives semen
3. passageway for fetus at parturition
• Vulva - extended genitalia; opening for both urinary and
genital tracts
WF-R ANIMAL SCIENCE 1
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
WF-R ANIMAL SCIENCE 1
Reproductive Functions (Female)
WF-R ANIMAL SCIENCE 1
Reproductive Functions (Female)
2. Estrus (heat, estrous period)
– Period of time when a female will accept a male in
copulation
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Reproductive Functions (Female)
3. Gestation
— Fertilization to parturition
— Develop embryo in uterus
4. Parturition
— Expel fully developed young at birth
5. Lactation
— Milk production
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Ovulation Rates
Ovulation Rates by Species
Cow1 egg per estrus
Ewe1 to 3 eggs per estrus
Sow10 to 20 eggs per estrus
Mare1 egg per estrus
HenApprox. 28 eggs per month
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Reproductive Terminology
Species
Cows
Ewes
Sows
Hens
Mares
Goats
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Act
Offspring
hatching
chick
Species
Cows
Ewes
Sows
Hens
Mares
Goats
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Act
calving
lambing
farrowing
hatching
foaling
kidding
Offspring
calf
lamb
pig
chick
foal
kid
Reproductive Functions (Female)
Gestation and Lactation Periods:
Species
Cow
Gestation Period
Lactation(Milking)
275 - 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
WF-R ANIMAL SCIENCE 1
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
WF-R ANIMAL SCIENCE 1
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
WF-R ANIMAL SCIENCE 1
The Male
Reproductive
Tract
Objective: Identify
the parts of the male
reproductive system
of livestock and
poultry
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Male Reproductive Tract
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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
WF-R ANIMAL SCIENCE 1
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
WF-R ANIMAL SCIENCE 1
Male Reproductive Tract
• Vas Deferens - slender tube from
epididymis to urethra which moves
sperm to the urethra
• Urethra - long tube from bladder to
penis; passageway for urine and sperm
out of the body
WF-R ANIMAL SCIENCE 1
Male Reproductive Tract
• Penis - male organ of copulation
which conveys semen and urine out
of the body
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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
WF-R ANIMAL SCIENCE 1
Male Reproductive Tract
• Cowper’s gland
• Also called the Bulbourethral gland
• Paired organs
• cleans the urethra prior to semen passage
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Male Reproductive Tract
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Reproduction in
Poultry
Objective: Specify how the
reproductive system for poultry
functions
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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, egg white
5) Infundibulum
– Where fertilization takes place
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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
• Takes about 26 hours for egg
to form
• Chicken Incubation
– 21 days
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Flip Book
• Create a Flip Book that shows how a poultry egg
develops
• Begin as an ovary
• Show the development through the oviduct
WF-R ANIMAL SCIENCE 1
Animal Reproduction and
Genetics
Objective: Describe the cell and
process involved in cell division
including how genes affect the
transmission of characteristics
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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
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Animal Cell
Nucleus
Cytoplasm
Cell
Membrane
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Animal Cell
• nucleus – gives cell ability to grow, to digest food
and to divide, contains chromosomes composed
of genes
• cytoplasm – gives the cell shape and contains
components necessary for cell functions
• cell wall – outside of cell
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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
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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
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Fertilization
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Chromosomes
• Rod shaped bodies
• Made of protein
• Found in the cell
nucleus
• Exist in pairs except
for gamete cells
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• The number of
chromosome pairs
differ for various
animals
–
–
–
–
–
Cattle 30
Swine 19
Horses 32
Chickens 39
Humans 23
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
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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
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Genes
Example:
The dominant gene is written- P
The recessive gene is written-p
P= Polled
p= horned
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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
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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
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Genotypes
• Three class genotypes
Homozygous Dominant = PP
Homozygous Recessive = pp
Heterozygous = Pp
• P = Polled & p = horned
• Six possible crosses:
PP x PP, PP x Pp, PP x pp, Pp x Pp, Pp x pp,
pp x pp
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Punnett Square
Polled Dam
P= Polled
p= horned
Example:
• Two polled cattle that are
homozygous for the polled trait
Genotypic Ratio: 4PP : 0
Phenotypic Ratio:4 polled animals
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Polled Dam
P
P
P
PP
PP
P
PP
PP
Punnett Square
Normal Dam
N= Normal size
n= Dwarfism
Example:
• Normal size in cattle is
dominant to dwarfism
Genotypic Ratio:
Phenotypic Ratio:
WF-R ANIMAL SCIENCE 1
Normal Dam
N
N
N
NN
NN
n
Nn
Nn
Punnett Square
N= Normal size
n= Dwarfism
Example:
• What if both parents are
carriers for a trait or
disorder?
Genotype:
Phenotype:
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Normal Dam
Normal Dam
N
n
N
NN
Nn
n
Nn
nn
Assignment
(Alternatives are horned and
red)
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Dam
Sire
Complete a Punnett
Square for two
animals that are
heterozygous for
two traits:
• Polled=P
• Black= B
Answer
Sire
A Punnett Square
Dam
for two animals
PB
Pb
pB
pb
that are
heterozygous for PB PPBB PPBb PpBB PpBb
two traits:
Pb PPBb PPbb PpBb Ppbb
• Polled=P
pB PpBB PpBb ppBB ppBb
• Black= B
pb PpBb Ppbb ppBb ppbb
(Alternatives are horned
and red)
WF-R ANIMAL SCIENCE 1
Heritability
• Objective:
– Discuss hertability estimates for beef and
swine
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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
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Heritability
• Swine rates are usually lower than cattle
• Heritiability for carcass traits are higher than
reproductive traits
• Estimates vary from 0 to 70%
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Birth weight
40%
Weaning Weight
25-30%
Yearling Weight
60%
Fertility
10%
Tenderness
60%
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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
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