wf-r animal science 1 animal reproduction and genetics

WF-R ANIMAL SCIENCE 1WF-R ANIMAL SCIENCE 1

Animal Reproduction and Genetics

WF-R ANIMAL SCIENCE 1

Terminology

• Objective:– Define terminology related to reproductive

management and breeding systems including castration, colustrum, estrus, gestation, lactation and parturition.


Terminology

• Castration- removing the testicles of male animals to prevent breeding.

• Colostrum- the first milk produced after a mammal gives birth that contains antibodies needed for immunity.

• Estrus- the time a female animal is receptive to be bred, also called heat.


Terminology

• Estrus Cycle- the length of a female’s cycle from one estrus to the next.

• Gestation- the time an animal is pregnant.

• Puberty- age at which animals reach sexual maturity and begin come into heat.


Terminology

• Lactation- the period of time that milk is secreted by the mammary glands.

• Parturition- the act of giving birth by female mammals.

• Ovulation- the release of the egg cell from the ovary.

• Fertilization- the union of the sperm and the egg cells.


Breeding Systems

• Objective– Discuss crossbreeding, grading-up,

inbreeding, linebreeding, and purebreeding


Breeding Systems

• Pure Breeding– Registered male and female animals– Angus X Angus


Breeding Systems

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


Breeding Systems

• Inbreeding– Mating closely related animals– Brother X Sister– Son X Mother– Father X Daughter


Breeding Systems

• Linebreeding– Breeding more distant relatives than

inbreeding– Cousin X Cousin


Breeding Systems

• Grading-Up– Mating purebred male (sires) to unregistered

or crossbred females (dams)– Yorkshire boar X Yorkshire/Hampshire sow– Hybrid Vigor

• Superior traits from crossbreeding • Offspring are better than parents


The Female Reproductive System

Objective: Identify the parts of the female reproductive system of livestock


Female Tract


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.


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



• 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.



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



• Cervix – Area between the

uterus and vagina

– Normally closed

– Opens at estrus and parturition

– (2 -3 inches)



• 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


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



2. Estrus (heat, estrous period)

– Period of time when a female will accept a male in copulation



3. Gestation— Fertilization to parturition— Develop embryo in uterus

4. Parturition— Expel fully developed young at birth

5. Lactation— Milk production


Ovulation Rates

Ovulation Rates by SpeciesCow- 1 egg per estrusEwe- 1 to 3 eggs per estrusSow- 10 to 20 eggs per estrusMare- 1 egg per estrusHen- Approx. 28 eggs per month


Reproductive Terminology

Species Act OffspringCowsEwesSowsHens hatching chickMaresGoats


Species Act OffspringCows calving calfEwes lambing lambSows farrowing pigHens hatching chickMares foaling foalGoats kidding kid



Gestation and Lactation Periods:

Species Gestation Period Lactation(Milking)

Cow 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



Estrous period length by species:

Cow 12 - 18 hours

Ewe 24 - 36 hours

Sow 48 - 72 hours

Mare 90 - 170 hours

Hens & Women none


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 How to AI a Cow


Summary

Specie Age Range at Puberty

Average Length of

Estrus Cycle

Average Length of

Estrus

Average Length of Gestation

Cow 6-8 months 21 days 16-18 hours 283 days

Swine 4-7 months 21 days 3 days 114 days

Sheep 4-8 months 22 days 30 hours 148 days

Goat 1st autumn 22 days 2.5 days 151 days


The Male Reproductive

TractObjective: Identify the parts of the male reproductive system of livestock and poultry


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



• Epididymis - Long coiled tube that is a path for sperm (connected to each testicle)

– Provide passageway for sperm out of the seminiferous tubules

– Storage for sperm – Place for sperm maturation



• 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



• Penis - male organ of copulation which conveys semen and urine out of the body, covered by a sheath



Accessory Glands:

– Seminal Vesicles • Function: Produce a fluid that protects and

transports sperm. • Description: A gland that opens into urethra.

– Prostate Gland • Function: Produces a fluid that is mixed with the

seminal fluid. • Description: Gland near the urethra and bladder.



• Cowper’s Gland– Function: Produces a fluid that moves

down the urethra ahead of the seminal fluid. It cleans and neutralizes the urethra to protect the sperm.

– Description: A gland near the urethra.


Reproduction in Poultry

Objective: Specify how the reproductive system for poultry

functions



• Ovary- poultry only have one functioning ovary as compared to livestock animals. – Function: Produces ova and hormones. The yolk of

an egg is the ovum. – Description: An attached cluster of yellow, round egg

yolks. • Infundibulum

– Function: The place where fertilization takes place.– Description: Funnel shaped structure located just

below the ovary. It is the start of the oviducts.



• Oviduct- tube like structure that consists of five parts:– Magnum- secretes the thick egg white or

albumen.– Isthmus- adds the two shell membranes.– Uterus- secretes the thin white, the shell and

the shell pigment.

– Vagina- holds the egg until it is laid.



• Cloaca– Function: Location where the papilla of the male bird

deposits semen. Egg also passes through this part. – Description: Located between vent and base of

oviduct. • Vent

– Function: Expel egg, liquid and solid waste. – Description: Outside opening to the poultry

reproductive tract.



• The major difference between mammals and poultry reproductive systems is that the embryo of livestock develops inside the female’s body and the poultry embryo develops outside the body. Papilla is the organ in male poultry’s cloaca wall that puts the sperm in the hen’s reproductive tract

• Chickens (domestic birds) have only the left ovary and oviduct functional at maturity (produce eggs). The right ovary and oviduct do not function.



• Egg- function is reproduction, but is eaten as food by humans and wild animals.

• Domestic chickens lay an egg every 24-28 hours regardless even if sperm are not present. Commercially sold eggs are not fertilized.

• Incubation time for chicken eggs is 21 days. • Turkeys and ducks eggs incubation is 28 days.


Animal Reproduction and Genetics

Objective: Describe the cell and process involved in cell division including how genes affect the transmission of characteristics


Parts of a cell

• Protoplasm- the material or contents inside of a cell.


Parts of a cell

• Cell Membrane- a thin layer of protein and fat that surround the cell. Some substances can pass into the cell and the membrane blocks others materials from entering.

Cell Membrane


Parts of a cell

• Centrosome- small body where the microtubules are made. The centrosome divides during mitosis.

Centrosome


Parts of a cell

• Nucleus- gives cell ability to grow, digest food and divide. Contains chromosomes and DNA.

Nucleus


Parts of a cell

• Cytoplasm- a jellylike substance that gives the cell shape and contains components necessary for cell functions.

Cytoplasm


Parts of a cell

• Golgi body- located near the nucleus and produces the membrane that surrounds the lyosomes.

Golgi body


Parts of a cell

• Lyosome- round shaped organelles that contain digestive enzymes that allow for digestion of cell nutrients.

Lysosome


Parts of a cell

• Mitochondrion- rod-shaped organelles that convert the energy stored in glucose into ATP (adenosine triphosphate). Mitochondrion


Parts of a cell

• Nuclear membrane- the membrane that surround the nucleus.

Nuclear membrane


Parts of a cell

• Nucleolus- organelle found inside the nucleus. Produced ribosomal RNA. Nucleolus


Parts of a cell

• Endoplasmic Reticulum- transports materials through the cell.

Rough ER

Smooth ER


Parts of a cell

• Vacuole- fluid filled membrane that fills with food and waste products inside the cell.

Vacuole


Parts of a cell

• Ribosome- site of protein synthesis.

Ribosome


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

cellsVideos: http://

www.youtube.com/watch?v=C6hn3sA0ip0http://www.youtube.com/watch?v=-DLGfd-Wpr4


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


Fertilization


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 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


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


Genes

Example:

The dominant gene is written- P

The recessive gene is written-p

P= Polled

p= horned


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


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


Genotypes

• Three class genotypesHomozygous Dominant = PPHomozygous Recessive = ppHeterozygous = 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


Punnett Square

P= Polled

p= horned

Example:• Two polled cattle that are

homozygous for the polled trait

Genotypic Ratio: 4PP : 0

Phenotypic Ratio:4 polled animals

P P

P PP PP

P PP PP

Polled Dam

Pol

led

Sir

e

Polled Dam

Pol

led

Sir

e


Punnett Square

N= Normal size

n= Dwarfism

Example:• Normal size in cattle is

dominant to dwarfism

Genotypic Ratio:

Phenotypic Ratio:

N N

N NN NN

n Nn Nn

Normal Dam

Sir

e C

arri

er

Normal Dam

Sir

e C

arri

er


Punnett Square

N= Normal size

n= Dwarfism

Example:• What if both parents are

carriers for a trait or disorder?

Genotype:

Phenotype:

N n

N NN Nn

n Nn nn

Normal Dam

Sir

e C

arri

er

Normal Dam

Sir

e C

arri

er


Assignment

Complete a Punnett Square for two animals that are heterozygous for two traits:

• Polled=P• Black= B

(Alternatives are horned and red)

Dam

Sir

e


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

Sir

e


Heritability

• Objective:– Discuss hertability estimates for beef and

swine


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


Heritability

• Swine rates are usually lower than cattle• Heritiability for carcass traits are higher than

reproductive traits• Estimates vary from 0 to 70%

• Traits with low heritability estimates are improved most through environment, and those traits with high heritability estimates are improved most by selective breeding and environmental improvements.


Birth weight 40%

Weaning Weight 25-30%

Yearling Weight 60%

Fertility 10%

Tenderness 60%


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

wf-r animal science 1 animal reproduction and genetics

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