Reproductive Structures and Cycles in Livestock Terminology Reproductive cyclicity –Provides...

Reproductive Structures and Cycles in Livestock

Terminology

• Reproductive cyclicity– Provides females with repeated

opportunities to become pregnant• Estrous Cycle

– Physiologic events that occur between periods of sexual receptivity and/or ovulations

• Estrus– Period of female sexual receptivity

Terminology

• Castration– Removing the testicles of the male to

prevent breeding

• Anestrus– Condition when females do not

exhibit regular estrous cycles

• Gestation– Time an animal is pregnant

Terminology

• Parturition– The act of giving birth

• Lactation– Period of time that milk is secreted

by the mammary glands

• Colustrum– First milk containing a high content

of antibodies providing temporary immunity to the offspring

The Female Reproductive System

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

Female Reproductive Anatomy

Female Tract

Suspensory Ligaments

• Broad Ligament– Supports and suspends tract– Provides vascular supply– Lymphatic drainage– Nerves

• Composed of:– Mesometrium (Body)– Mesosalpinx (oviduct)– Mesovarium (ovary)

Suspensory Ligaments

Ovary

• Female gonad comparable to the male testicle – Site of gamete production– Bovine have 20,000 potential eggs (ova)

per ovary, humans have 400,000 potential eggs per ovary

– Ova are fully developed at puberty and are not continuously produced as in the male

– The hen has only a left functioning ovary

Ovaries Continued

• Suspended by mesovarium• Shape varies by species

– Cattle-almond shaped– Horses- bean shaped– Sheep- round– Swine- lobular

Functions of the Ovaries

• 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

Oviducts (Fallopian Tubes)

• Pair of small tubes leading from the ovaries to the horns of the uterus– Site of fertilization– Supported by mesosalpinx– 3 to 4 days for egg to travel down

oviducts• Infundibulum - funnel shaped portion of

the fallopian tube that catches the ovulated egg

Oviducts (Fallopian Tubes)

• Functions:– Ovum transport– Sperm storage and capacitation– Fertilization – Early embryo development

Female Reproductive System

ovary

infundibulum

uterus

Uterus

• Muscular sac connecting fallopian tubes and cervix

• Consists of a body and two horns– Cow, ewe, and mare (bicornuate)– Sow has only horns, no body– Woman has no horns (simplex)

Female Reproductive System

Uterus Functions

• Sustains sperm and aids in its transport

• Maternal placenta - supports embryo and fetus during gestation

• Expels fetus at parturition • Control of cyclicity

Cervix

• Area between the uterus and vagina• Normally closed; opens at estrus and

parturition • Functions:

– Lubrication– Flushing– Barrier to foreign material or bacteria

Cervix – Species Differences

• Cow and ewe - annular rings

• Sow - corkscrew• Mare - longitudinal

folds

Vagina and Vulva

• Vagina: connects the cervix to the external genitalia and serves as the female copulatory organ

• Vulva: external tissue of the female reproductive tract, receives penis during copulation

Reproductive Tract of Cow

Reproductive Tract of the Ewe

Reproductive Tract of the Mare

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

Ovulation Rates by Species

Species Ovulation Rate

Cow 1 egg/estrus

Ewe 1 - 3 eggs/estrus

Sow 10 - 20 eggs/estrus

Mare 1 egg/estrus

Hen ~ 28 eggs/month


2. Estrus (heat) – 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

– Estrus detection methods: visual inspection, teaser animals, marker aids

Types of Cyclicity

• Polyestrus - uniform distribution of estrous cycles occurring regularly throughout the year– Cow, sow

• Seasonal Polyestrus - “periods” of estrous cycles occurring only during certain seasons of the year– Sheep, goat, deer, mare

• Monoestrus - only one cycle per year, often lasting several days– Dogs, wolves, bear, fox

Timing of Events in the Reproductive Cycle

Species Length of Estrous Cycle

Duration of Estrus

Time of ovulation

Ewe 17 days 24-36 hours 24-30 hrs from estrus onset

Goat 21 days 32-40 hours 30-36 hrs from estrus onset

Sow 21 days 48-72 hours 35-45 hrs from estrus onset

Cow 21 days 18-19 hours 10-11 hrs after onset of estrus

Mare 21 days 4-8 days 1-2 days before end of estrus


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

4. Parturition— Expel fully developed young at birth

5. Lactation— Milk production

Reproductive Terminology

Species Act Offspring

Cow calving calf

Ewe lambing lamb

Sow farrowing piglet

Hen hatching chick

Mare foaling foal

Goat kidding kid

Gestation and Lactation Periods

Species Gestation Period (days)

Lactation Period (days)

Cow 275 - 285 beef 180 - 270 dairy 305 - 365

Ewe 115 - 142 60 - 90 - 120

Sow 112 - 115 21 - 42

Mare 330 - 345 90 - 150

Woman 270 ? (years)

The Male Reproductive Tract

Objective: 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 – Maintains sperm 4-5oF cooler than

the body temperature • Testicles - primary male organs of

reproduction – Produce sperm – Secrete testosterone

Cryptorchidism

• Failure of one or both testes to descend into the scrotum– Unilateral: one testis does not

descend •testis that descends is fertile;

reduced sperm concentrations

– Bilateral- neither testes descend into scrotum•Results in sterility due to elevated

temperature of both testes

Testicle Anatomy


• 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– Moves sperm to the urethra at

ejaculation • 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

• Penis retractor muscle - allows extension and retraction of the penis; sigmoid flexure extends in copulation

Fibroelastic vs. Vascular Penis

• Fibroelastic: erection extends the length of penis rather than diameter– Bull, Ram, Boar

• Vascular: composed of specialized tissues that fill with blood causing the penis to become turgid during erection – Stallion


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 – Gives semen it’s characteristic odor


• Cowper’s gland•Also called the Bulbourethral

gland•Paired organs •cleans the urethra prior to semen

passage

Differences in Tracts

• Bulls- Pendulous, perpendicular testes• Ram- Pendulous, perpendicular testes;

Filiform appendage• Boar- Inverted testes; No ampulla;

corkscrew penis; much larger bulbourethral gland

• Stallion-Horizontal testis; loosely attached tail of epididymis; Smooth seminal vesicles; no sigmoid flexure

Bull Reproductive Tract

Ram Reproductive Tract

Boar Reproductive Tract

Stallion Reproductive Tract

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

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• Chicken Incubation

– 21 days

Reproductive Structures and Cycles in Livestock Terminology Reproductive cyclicity –Provides...

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