Maharashtra Board Class 11 Animal Science And Technology Chapter 12 Reproductive Technologies PDF Download

12. Reproductive Technologies

Can you recall?

The terms sperm, ovum, estrous, fertilization and parturition.

How the reproduction takes place in animals?

12.1 Basics Of Reproduction

12.1.1 Estrous Cycle

Estrous cycle is the chain of physiological events that begins at one estrous period and ends at the next.

The estrous cycle consist of a long luteal phase (days, 1-17) where the cycle is under the influence of progesterone and shorter follicular phase (days, 18-21) where the cycle is under the influence of estrogen and can be completed in four stages.

1. Follicular Phase (Days, 18-21) i) Proestrus stage. ii) Estrus stage.

2. Luteal Phase (Days, 1-17) i) Metestrus stage. ii) Diestrus stage.

The details of various stages of estrous cycle are as follows.

1. Proestrus: It is the initial stage of estrous cycle. It usually lasts for 2 to 3 days in cow. It is characterized by follicular growth in ovaries and production of estrogen.

2. Estrus: It is the period of sexual desire. The duration of this stage in cows is around 24 hours. The ovary presents mature Graafian follicle. There is high level of estrogen in blood. The animal exhibits signs of heat during this stage.

3. Metestrus: It is the period after estrus. It lasts for 2-3 days in cows. It is characterised by cessation of visible signs of heat. The Graafian follicle ruptures and ovulation takes place during this period in cows and buffaloes. The ruptured follicle in the ovary is replaced by small, soft, developing corpus luteum which secretes a hormone called as progesterone.

4. Diestrus: It is the longest stage of estrous cycle. It usually lasts for 15 days in cow. The corpus luteum fully develops. This stage is followed by either pregnancy or next estrous cycle or anestrous in animals.

Remember...

Heat/estrus is the period of intense sexual desire or sexual excitement experienced by females.

Teacher's Note

Heat is when a cow wants to have babies. Like when your mother is ready to cook food, the cow is ready to have a baby at this time.

Exam Trick

Remember: Estrus = Heat = Cow wants baby. Diestrus = Longest stage = Like waiting for the bus for the longest time.

Points to Remember

Estrous cycle has four stages: Proestrus, Estrus, Metestrus, and Diestrus.
Estrus is when the cow shows heat and wants to have babies.
Progesterone hormone is made during Metestrus stage.
Diestrus is the longest stage and can last for 15 days in cows.
Heat is the time when a female animal wants to make babies.

Symptoms of heat/estrus

The cows in heat exhibit signs of excitement, restlessness, reduced appetite and rumination, frequent bellowing, drop in milk production, swollen and congested vulval lips, licking other animals, frequent urination with raised tail, peculiar movement of back and clear, shiny, stringy vaginal mucous discharge. Cows in heat attempts to mount other cows and also stands to be mounted when other cow/animal mounts.

Teacher's Note

Different animals have different heat cycles. A cow has heat every 21 days, but a goat has heat every 20 days. This is like how different students in your class wake up at different times.

Exam Trick

Remember: Cow = 21 days, Buffalo = 21 days, Ewe = 17 days, Doe = 20 days. Just remember these numbers by their pattern!

Points to Remember

Cows and buffaloes have estrous cycle of 21 days.
Ewes have shorter cycle of 17 days.
Gestation period in cow is 280 days (about 9 months).
Gestation period in buffalo is 310 days (about 10 months).
Buffalo breeding season is from September to February.

Observe and record...

The behaviour of cow and buffalo during heat/estrus.

12.1.2 Fertilization

Fertilization is the union of male and female gametes.

Ovum: Ovum is a female gamete. It is produced in the ovary by oogenesis. It is roughly spherical, non-motile structure. It is covered by vitelline membrane, zona pellucida and cells of cumulus oophorus / corona radiata.

Sperm: Sperm is a male gamete. It is produced in the testis by spermatogenesis. It is microscopic, motile structure. It consist of head, neck, middle piece and elongated tail.

Process of fertilization

The process of fertilization involves following steps.

1. Transport of sperm: Sperms deposited in the female genital organ either by natural service or artificial insemination are transported to the site of fertilization (ampulla) by both sperm motility and contractions of female genital tract.

2. Capacitation: When the sperms are exposed to female reproductive tract for 4-6 hours, they attain the capacity to penetrate and fertilize the ovum. This process of preparing the sperms for fertilization is known as capacitation.

3. Ovulation: Under the effect of LH, the matured Graafian follicle from ovary ruptures and the ovum is released. This process of release of ova is called as ovulation. Ovulation usually takes place about 8 hours after the end of estrus in cows. The released ovum is immediately picked up by infundibulum and reaches the ampulla in another 6 hours.

Do you know?

The sperm remains viable for 24 hours in female genital tract whereas, ovum remains fertile for only 10 hours after ovulation.

Teacher's Note

Fertilization is like when a father and mother come together to make a baby. The sperm from father meets the ovum from mother, and then a baby starts growing.

Exam Trick

Remember: Capacitation = Training of sperm. Like training a soldier before he goes to war, sperms are trained before they try to make a baby.

Points to Remember

Fertilization is the joining of sperm and ovum.
Capacitation is when sperms get ready for 4-6 hours in the female body.
Ovulation happens about 8 hours after the end of heat in cows.
Sperm lives for 24 hours but ovum lives for only 10 hours.
Ampulla is the place where sperm meets ovum.

This is a preview of the first 3 pages. To get the complete book, click below.