Reproductive anatomy and physiology

1. Reproductive anatomy and physiology Animal Science II Fall 2013

2. Summary - Anatomy • Reproductive Management Terminology and Traits • 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. • 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. • 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.

3. Summary - Anatomy Reproductive Traits

4. Summary - Anatomy • Parts & Functions of the Female Livestock Reproductive System • Ovaries • Function: Produce ova called eggs. • Description: Two oval shaped organs located near the end of the reproductive tract inside the body cavity. • Oviducts • Function: Carry the eggs from the ovaries to the uterus. Also called fallopian tubes. • Description: Small tubes that are near but not attached to ovaries and have a funnel-shaped end near the ovary. • Infundibulum • Function: Picks up eggs at ovulation and directs eggs into the oviduct. • Description: Funnel-shaped end of each oviduct near the ovary. • Uterus • Function: Also called womb, place where fetus grows and develops. • Description: Organ with two branched horn-shaped attachments called uterine horns. Will have a baby inside if animal is pregnant.

5. Summary - Anatomy • Parts & Functions of the Female Livestock Reproductive System • Cervix • Function: Serves as a passageway for sperm to travel from the vagina to the uterus. Also seals the uterus during pregnancy to prevent pathogens from affecting fetus. • Description: Thick walled structure made up of folds and rings of muscular tissue. Located at the neck of uterus. Separates the uterus from the vagina. • Vagina • Function: Receives the male penis and sperm at breeding. Also serves as a passageway for the baby to pass through at birth and is a passageway for urine to be expelled. • Description: Connects the vulva to the cervix. • Vulva • Function: External opening to female reproductive and urinary systems. • Description: External opening made up of folds of skin.

6. Summary - Anatomy • Livestock and Poultry Male Reproductive Parts • Scrotum • Function: Holds and protects testicles. • Description: Saclike part outside livestock that holds testicles. • Testes or Testicles • Function: Produce sperm and male sex hormones. • Description: Two oval meaty type structures inside scrotum in livestock and inside body cavity of poultry on each side of backbone. • Epididymis • Function: Stores sperm while they mature. • Description: Long coiled tube connected to each testicle. • Vas Deferens • Function: Serves as a passageway for sperm to travel from the epididymis to the urethra. • Description: Tube that connects the epididymis to urethra.

7. Summary - Anatomy • Livestock and Poultry Male Reproductive Parts • 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. • Penis • Function: Deposits semen in female animals. Papilla serves this function in poultry • Description: Rod like tissue covered by sheath. • Sheath • Function: Protects penis from injury. • Description: Skin that covers the penis.

8. Summary - Anatomy • Poultry Reproductive System • 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.

9. Summary - Anatomy • Parts and Functions of the Poultry Reproductive System • 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.

10. Summary - Anatomy • Parturition of Animals • If an ovum of the female animal is fertilized and the animal becomes pregnant, the embryo begins to grow and develop. • After a period of embryological development, the developing animal is referred to as a fetus. • During gestation, the fetus develops in the uterus. • At the end of the gestations period, parturition begins. • Normal position of the fetus at birth: • Front feet first with legs slightly offset from each other to allow for shoulders to pass through birth canal. • Nose tucked between front legs. • Shoulders. • Body or middle of animal. • Hips. • Back legs and feet.

11. Summary - Anatomy • Parturition of Animals • Any presentation (position at birth) that does not have the order stated above is abnormal and could cause problems as severe as death of the newborn animal and/or the mother. • Parturition Process • Begins when increased estrogen causes the uterus muscles to contract. • First water bag appears, enlarges and breaks open. • Soon afterwards, the second water bag containing the fetus breaks open and the presentation of the calf begins. • Several hours later, the placenta and other membranes (afterbirth) are expelled. If afterbirth is not expelled, the animal will become sick.

12. Summary – Physiology • Female Livestock Reproductive Physiology • Estrous Cycle- the length of the animal’s reproductive cycle from one estrus to the next. Typical estrous cycle for cattle and swine is 21 days. • Estrus- period of receptivity to the male. The actual time a cow is in heat is about 16-18 hours, and a sow is in heat about 2 days. Signs of heat differ for various livestock animals. • Cattle- swelling of the vulva, frequent urination, nervousness or restlessness, mounting other animals and letting other animals mount. The best indication that a cow is ready to breed is when she stands when mounted by another cow. • Swine- restless activity, swelling of the vulva, discharge from the vulva, frequent urination and occasional loud grunting.

13. Summary – Physiology • Ovulation- release of ova (egg) from ovary at the beginning (day 1) of female’s cycle. • Ovaries produce ova and the sex hormones estrogen and progesterone. • Number of young that animals give birth to at one time is indication of number of eggs released or ovulated. • Sows- 10-15. • Cows- 1. • Each ovary houses hundreds of follicles where ova develop. • The largest follicle is usually the one that is ready for ovulation. • Forms the corpus luteum shortly after ovulation. • Corpus luteum releases hormone progesterone. • If sperm are not present, the corpus luteum does not persist.

14. Summary – Physiology • Estrogen- released by cells lining the follicle. • Transported in the blood stream and causes numerous reactions in the animal’s body: • Increases sensitivity in the uterus. • Aids in the transport of semen. • Mucus secretion in the cervix to lubricate the vagina. • Signals signs of heat displayed by the animal. • Progesterone- produced 5-6 days after ovulation and released by cells in the corpus luteum. • If sperm were present during ovulation and fertilization occurred, progesterone: • Stops other eggs from forming and prevents estrus while animal is pregnant. • Regulates production of follicle stimulating hormone (FSH) and lutenizing hormone (LH). • Allows egg to implant in the uterus. • Maintains pregnancy. • Encourages development of mammary glands.

15. Summary – Physiology • If fertilization does not occur because sperm were not present or the body did not recognize the pregnancy, between day 15-16 the hormone prostaglandin: • Stops production of progesterone and destroys the corpus luteum. • Stimulates increase release of follicle stimulating hormone (FSH) and lutenizing hormone (LH) from the pituitary gland in the brain and the animal will continue the estrous cycle in preparation for the next heat and ovulation. • FSH stimulates growth of follicles. • LH stimulates estrogen production which brings animal back into estrus.

16. Summary – Physiology • Embryo and Fetal Development • Day 1-2- spermatozoa travel into reproductive tract and ova is released and travels from ovary to oviduct through the infundibulum so fertilization can occur. • The fertilized ovum is now referred to as a zygote and travels towards the uterus during the first 4-5 days of the estrous cycle. Uterine fluids surround the zygote. • The animal’s body sends chemical signals to maintain levels of progesterone and retain the corpus luteum. • The zygote continues to float freely in the uterus and develop membranes that become the placenta. • Placental attachment occurs around day 30 in the cow and the embryo continues to develop for the remainder of the gestation period. • Near the end of gestation, the corpus luteum reduces production of progesterone which causes an increase in estrogen production. • Estrogen along with other hormones stimulates contractions which begins the birthing process.

17. Summary – Physiology • Parturition- occurs in 3 phases • Preparatory Stage- females prepares to give birth. • Shows signs of restlessness, raising tail, separation from other animals and mucus discharge. • Mild uterine contractions may be observed. • Fetus rotates to birthing position. • Cervix begins to dilate and the some part of fetus enters birth canal depending on fetal presentation (front legs, rear legs, etc.). • Some fetal membranes may be visible when examining vulva.

18. Summary – Physiology • Parturition- occurs in 3 phases • Expulsion Stage- fetus is expelled. • Uterus increases frequency and force of contractions. • Fetus is in birth canal and delivery should occur quickly. • Presentation of fetus varies between species: Cattle- front feet, nose, head, shoulders, body, hips and back legs. • Swine- no set presentation. • Dystocia- an abnormal or difficult birth. Causes: • Animals that do not enter the birth canal in a normal presentation. • Selection of animals with larger frame size than the female can manage. • Cleaning Stage- expelling afterbirth. • Retention of afterbirth will lead to infection and potentially death of the mother. • After proper cleaning the uterus shrinks back to normal size (involution) and animal begins to cycle again.