Reproduction in Livestock Animals

Reproductive organ

Gonads

What is the female gonad?

Ovary

What is the male gonad?

Testis 

What are the two primary functions of gonads?

Steroidogenesis and gametogenesis

The production of the sex hormones 

Steroidogenesis 

The production of gametes, i.e. sperm and egg

Gametogenesis 

Maturity of the sexual organs

Puberty

Associated with the secondary sex characteristics (Ex. humps on the neck of bulls; mammary development in females

Puberty

Initiated by the hypothalamus 

Puberty 

What hormone is released by the hypothalamus to initiate puberty?

Gonadotropin-releasing hormone (GnRH)

In response to GnRH the anterior pituitary gland releases these two hormones

Luteinizing hormone (LH) and Follicle stimulating hormone (FSH)

Gonadotropins 

Luteinizing hormone (LH) and Follicle stimulating hormone (FSH)

Where does Luteinizing hormone (LH) and Follicle stimulating hormone (FSH) travel?

Gonads

Are Luteinizing hormones (LH) and Follicle stimulating hormone (FSH) found in females or males?

Both

Male or Female: Release of LH is the signal to the testes to produce testosterone, the primary male sex hormone

Male 

This hormone is required for sperm production

Follicle stimulating hormone

Male gamete

Sperm

Female gamete

Ova (egg)

This hormone is responsible for the growth and maintenance of the developing follicle that is destined to produce the ova

Follicle stimulating hormone

What hormone do growing follicles produce?

Estrogen

What causes ovulation?

Increased level of estrogen that causes a surge of Luteinizing hormone

An increased level of estrogen causes a surge of LH to be released from the pituitary gland leading to ____

Ovulation

The ovaries of the newborn female contain all of the ____ the female will ever have

Oocytes (gametes)

What contains the oocytes in females?

Primordial follicles

Starting at puberty, the primordial follicles grow and develop what for every monthly cycle?

Folliculogenesis

Site of fertilization

Oviduct

How long does the egg remain in the oviduct before traveling to the uterus?

3-6 days

Follicles (with oocytes/eggs) are developing in the ovaries

Follicular phase

Following ovulation, Corpus luteum (CL) is producing high concentrations of progesterone to maintain uterine quiescence

Luteal phase

Demis of the CL; progesterone decreases

Luteolysis

What are the two phases of the Estrous Cycle?

Follicular and Luteal phase

Release of the ova from the ovary

Ovulation

Functions of the Uterus (5)

Passageway for sperm cells, nourishment for the embryo prior to development of the placenta, suitable environment for the development of the fetus, provides nutrients and eliminates waste products for the developing fetus through the placental uterus junction, expulsion of the fetus during parturition 

Functions of the cervix and vagina (5)

Passageway for sperm cells, storage reservoir for sperm cells, primary barrier for pathogens for the exterior, lubrication, passageway for the fetus at parturition

The vagina serves a dual function

Copulatory organ and birth canal

Responsible for both gamete (sperm) production and production of the male sex steroids 

Testes D

Begin development in the abdominal cavity but descend from the abdomen to the scrotum

Testes

Where do testes initially develop before the drop?

Abdominal cavity

One or both testes may have not descended

Cryptorchidism 

Protects the tetes and allows quick cooling to maintain proper temperature (4 to6 degrees cooler than body temperature)

Scrotum

Produced by seminiferous tubules in the testis

Sperm

Sperm is stored here

Epididymis 

Transports the sperm from the epididymis to the urethra

Ductus deferens (Vans deferens)

Add fluid to the sperm to make up the final product, semen

Accessory sex gland

What are the three accessory glands?

Seminal vesicles, prostate gland, bulbourethral glands

Increases the volume, add nutrients, and aid in coagulation of the semen after ejaculation

Accessory sex glands

Deposits the semen in the vagina or cervix, depending on the species

Penis

Two types of penises

Vascular and Fibroelastic 

Vascular penis

Stallions

Fibroelastic penis

Bull, boars, rams

Specialized erectile tissue retains blood during sexual excitement; erection develops

Vascular

Penis resides in an S shaped configuration inside the body until erection and extends through the sheath during sexual excitation

Fibroelastic

Straightening of the sigmoid flexure resulting in increased length and no change in penile diameter during sexual excitation

Fibroelastic

The oocyte begins to degenerates if not fertilized in how long?

12 hours

One celled embryo; once an oocyte is fertilized

Zygote

Multi celled embryo

Morula

Further development of the morula turns into ____

Blastocyst

The inner cell mass of the blastocyst becomes what?

Fetus

The trophoblast parition develops into what?

Placenta

The placenta develops from what?

Trophoblast

The fetus develops from what part of the blastocyst?

Inner cell mass

Breakdown or degeneration of the CL; occurs at the end of the luteal phase of the estrous cycle

Luteolysis

Cell that results from the fusion of the sperm and oocyte

Zygote

Early-state embryo, after cell division multiplies cell numbers in the zygote

Morula

Differentiating embryo consisting of an inner cell mass, blastocoele and trophoblast

Blastocyst

Group of fatty acids hormones which breaks down the CL allowing return to estrus (only in cows and ewes)

Prostaglandin 

During pregnancy the CL produces high levels of this?

Progesterone

What is required to maintain pregnancy?

Progesterone

Produces proteins that block the demise of the CL (maternal recognition of pregnancy)

Blastocyst

Four components of the fetal membrane

Amnion, yolk sac, allantois, chorion

Surrounds and cushions the fetus in amniotic fluid

Amnion

Provides nutrients to the developing embryo/fetus

Yolk sac

Gas exchange, waster removal

Allantois

Outermost fetal membrane, protection

Chorion

Regulates the exchange of oxygen, nutrients, waste, and in some species antibodies, between the mother and fetus

Placenta

When more than one fetus is present, the membranes of the fetuses typically fuse together

Anastomosis

Anastomosis does NOT have a normal fetal development in what animal?

Cow

If anastomosis occurs with a bull and a heifer what happens?

Female is born sterile (Freemartin)

Two thirds of fetal development occur in what trimester?

Last

Aka lambing or kidding sickness, ketosis

Pregnancy toxemia

Most prevalent metabolic disease in sheep- low glucose; fat burned for fuel 

Pregnancy toxemia 

What are the two types of pregnancy toxemia?

Under nutrition (chronic) syndrome and Stress (acute) syndrome

Results of pregnancy toxemia (3)

Nervous system dysfunction, muscle weakness, fetal death in utero

How much more feed do ewes/goats need to prevent toxemia if carrying a SINGLE lamb?

50%

How much more feed do ewes/goats need to prevent toxemia if carrying TWINS?

75%

Length of Cow pregnancy

283 days

Length of doe pregnancy

150 days

Length of ewe pregnancy

147 days

Length of sow pregnancy

114 days

Process of giving birth 

Parturition 

Difficulty in birthing

Dystocia

Behavioral changes of parturition

Restlessness, isolation, and extreme discomfort

Physical changes of parturition 

Swelling of the vulva, engorgement of the udder, relaxation of the ligaments around the tailhead

Waterbag

Allantochorion

Antibodies contained in the first milk

Colostrum

What does colostrum provide?

Passive immunity

Period between parturition and the onset of estrous activity

Postpartum