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 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


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


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 Hereford = Crossbreed


Breeding Systems

– Hybrid Vigor• Superior traits from crossbreeding • Offspring are better than parents


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– Can be traced back to a common ancestor,

such as a grandparent – Cousin X Cousin


Breeding Systems

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

or crossbred females (dams) to improve herd– Yorkshire bore X Yorkshire/Hampshire sow


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 daysdairy 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


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

– Provide passageway for sperm out of the seminiferous tubules

– Storage for sperm

– Fluid secretion to nourish 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



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



• Cowper’s gland• Also called the Bulbourethral gland• Paired organs • cleans the urethra prior to semen passage




Reproduction in Poultry

Objective: Specify how the reproductive system for poultry

functions




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







• 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


Flip Book

• Create a Flip Book that shows how a poultry egg develops

• Begin as an ovary • Show the development through the oviduct


Animal Reproduction and Genetics

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


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


Animal Cell

Nucleus

Cytoplasm

Cell Membrane


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


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


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%


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

Date post:	05-Feb-2016
Category:	Documents
Upload:	roden
View:	54 times
Download:	3 times

Animal Reproduction and Genetics

Documents