Animal Reproduction

ANIMAL REPRODUCTION

A. Male reproductive system – Bull or Ram

1. Scrotum – saclike part that contains testicles and the epididymis; keeps temperature lower to keep animal fertile

2. Testicles – produce the sperm cells and the male hormone testosterone

3. Epididymis – stores sperm cells while they mature

4. Vas deferens – passage way from epididymis to the urethra

5. Spermatic cord – protective sheath for vas deferens

6. Urethra – passageway for urine from the bladder and where sperm from the epididymis is mixed with fluid from accessory glands to form semen

7. Seminal vesicles – produces a fluid which protects and transports the sperm

8. Prostate gland – produces a fluid that is mixed with a seminal fluid.

9. Cowper’s gland – produces a fluid which cleans and neutralizes the urethra ahead of the seminal fluid to help protect the sperm

10. Penis – deposits the semen within the female reproductive system

1 11. Sigmoid flexure – extends the penis from the sheath

12. Sheath – tubular fold of skin

13. Retractor muscle – draws the penis back into the sheath after copulation

2 B. Female reproductive system – Cow or Ewe 1. Ovaries – produce the eggs within the follicles, produce the female sex hormones estrogen and progesterone, and form the corpus luteum

2. Infundibulum – funnel like end of oviduct closest to the ovary

3. Oviducts (fallopian tubes) – carry the eggs from the ovaries to the uterus

4. Uterus (womb) – place where the fetus grows; it has two horns or branches

5. Cervix – is the neck of the uterus which separates the uterus from the vagina

6. Vagina – passage between the cervix and the vulva; semen is deposited here during copulation

7. Vulva – external opening of the reproductive and urinary system

8. Clitoris – sensory and erectile organ of the female

C. Reproductive systems of poultry  Male chicken 1. Testicles – produce the sperm and seminal fluid

2. Vas deferens – carry the seminal fluid and sperm cells to the cloaca

3 3. Cloaca – is enlarged part where the large intestine joins the end of the alimentary canal

4. Alimentary canal – is the food-carrying passage which begins at the mouth and ends at the vent

5. Papillae – is the organ in the wall of the cloaca that puts the sperm cells into the hen’s reproductive tract

4  Female chicken 1. Ovary – produces the egg; only the left ovary and oviduct produce eggs; the ova produced in the ovary develop into egg yolks

2. Funnel – receives the yolk from the ovary and stores sperm cells

3. Magnum – secretes the thick white of the egg (takes about 3 hours)

4. Isthmus – two shell membranes are placed around the yolk and thick white (takes about 1 hour & 15 minutes)

5. Uterus – the thin white and the outer shell are added here; the egg remains in the uterus for about 20 hours

6. Vagina – the completed egg remains here for a short period of time before being laid

A. Heat Period – time that the cow is receptive to the bull  Signs of heat include: 1) Cattle, swine, and goats – a) Trying to mount other animals and standing when mounted by other animals b) Nervousness and restless activity c) Swelling of the vulva d) Inflamed appearance around the lips of the vulva e) Frequent urination f) Mucus discharge from the vulva 2) Horses – a) Relaxation of the vulva

5 b) Frequent urination c) Teasing of other mares d) Apparent desire for company e) Slight mucus discharge from the vulva 3) Sheep – exhibit many of the same signs, but not quite as visible as other species of livestock; are seasonal breeders

B. Ovulation – release of egg from ovary 6. Before ovulation, the egg cell is contained in the follicle that breaks open, releasing the egg. 7. The egg moves into one of the oviducts where if live sperm is present, the egg may be fertilized. 8. Shortly after ovulation, the corpus luteum forms on the ovary that releases the hormone progesterone. Progesterone causes four things to happen: a. The fertilized egg is implanted in the uterus b. Other eggs are stopped from forming c. The pregnant condition is maintained d. The mammary glands begin to develop, which produce milk to feed the young when they are born.  If the egg is not fertilized, it does not grow. It atrophies, or wastes away which allows another follicle to grow and another heat period to occur.

C. Fertilization – is the union of the sperm and the egg cells  During copulation, the male deposits sperm in the reproductive tract of the female where the sperms move through the tract until they reach the infundibulum.  If an egg is present, a sperm cell may penetrate it.  Only one sperm cell fertilizes an egg cell.

6  Sperm cells cannot live very long in the female reproductive tract (24-30 hours in cattle).  The egg cell lives about 12 hours after it is released if it is not fertilized.  For fertilization to occur, live sperm cells and the egg cell must be present at the same time.  If fertilization does not occur, the body absorbs the egg and sperm cells. The estrus cycle will repeat itself until the animal does become pregnant.

D. Gestation – is the time when an animal is pregnant and the fetus is developing in the uterus.  The fetus is connected to the placenta by the umbilical cord.  The placenta allows food, oxygen, and wastes to be exchanged with the mother by the diffusion process.  The fetus develops slowly in the first third of pregnancy with the nervous system, head, and blood vessels developing first followed by the bones and limbs.  Average length of gestation: 1. Cattle – 281 days 2. Sheep – 148 days 3. Swine – 114 days (3 months, 3 weeks, & 3 days) 4. Goats – 151 days 5. Horses – 336 days

E. Parturition – is the process of giving birth to the new animal  The corpus luteum reduces the production of progesterone and there is an increase in the amount of estrogen in the body.  This causes the uterine muscles to contract which begins the process of birth: 7 1. The first water bag gets larger and breaks 2. Shortly thereafter, the second water bag appears & breaks open 3. Presentation of the fetus begins (front feet first, followed by nose, then head, shoulders, middle, hips, rear legs, and feet appear) 4. Young must receive colostrum (first milk) for first 12 to 14 hours 5. Several hours after birth the afterbirth (placenta) is expelled from the uterus

F. Reproduction in poultry is different than mammals in that the young are not carried in the hen’s body, but instead develop in the fertilized egg outside of the hen’s body. The process involves the following steps: 9. The papillae in the cloacal wall of the male deposits the sperm in the cloacal wall of the female. 10. The sperm moves up the oviduct to the funnel of the oviduct where the egg is fertilized. 11. After the egg yolk is fertilized, it moves through the reproductive tract of the female where the thick white, shell membranes, thin white, and the shell are added. 12. After the egg is laid, the embryo grows inside the shell. The embryo is fed by the contents of the egg during development. 13. Incubation of eggs is keeping them at the proper temperature and humidity for hatching (102 to 103 degrees F). 14. After incubation, the chicken hatches or breaks out of the shell (21 days for chickens). G. Cryptorchidism  Is an inherited trait in males where one or both testicles are held in the body cavity. 8  The animal is usually sterile if both testicles are in the body cavity.