Ag science-chp 23 animal reproduction

Give a function for each:

1) ovary

2) oviduct/fallopian tube

3) uterus

4) cervix

5) vagina

1) produces eggs

2) connects ovary to uterus, fertilisation.

3) growth of embryo (muscle can contract and expand)

4) dilates at parturition (birth)

5) birth canal, holds penis during copulation

Give a function for each:

1) testes

2) scrotum (sack)

3) epididymis

4) vas deferens (sperm duct)

5)-seminal vesicle

-prostate gland

-cowpers gland. (respect)

6) penis

1) production of sperm

2) lower temperature, allows sperm to develop

3) sperm produced in testes is stored here

4) sperm travels in

5) produces seminal fluid

6) ejaculation of sperm into the vagina

Explain each female hormone

1) follicle stimulating hormone (FSH)

2) oestrogen

3) luteinising hormone (LH)

4) progesterone

5)prolactin

1) stimulate growth of follicle

2) stimulate the growth of the endometrium

3) ovulation

4) maintain gestation and inhibit labour and lactation prior to birth

5) for lactation, milk let-down (colostrum is the first milk), made from the pituitary gland(dairy cow)

Explain each male hormone

1) follicle stimulating hormone(FSH)

2) luteinising hormone (LH)

3) testosterone

1) sperm production

2) stimulates testosterone production

3) male sex characteristics as well as increasing muscle and bone growth

Methods of fertilisation 1 artificial insemination

•semen is collected from bull

•straws frozen and stored in liquid nitrogen at -196°C

•when farmer detects cows in heat straws thawed in warm water

•straw is placed in catheter(narrow flexible tube)

•Ai technician places hand inside cows rectum until they feel the cervix of the uterus

•catheter is guided through cervix into uterus and semen is deposited in uterus of cow

Advantages of AI

1) prevents the spread of std’s

2)cost of ai straw is little in comparison to purchasing, feeding and housing a bull

3) wide variety of bulls allows the farmer to target specific genetic traits within the herd

Disadvantages of AI

1)successful heat detection is crucial

2) more labour and management skills required (than natural service by a bull)

3) semen must be stored properly otherwise it will not be viable ( won’t be able to fertiliser anything)

4) a stock bull may be required for mopping up at the end of the breeding season

Methods of fertilisation 2 sexed semen

•used to increase the chance of a heifer calf being born

•in dairy herds heifer calf’s are more desirable than bull calves since calves can be used as replacements to expand the dairy herd

•with stock bull/ai there’s only 50% chance of a heifer calf being Alf being born

•with sexed semen bulls can be separated into 2 groups, sperm carrying Y chromosome (male) and sperm carrying X chromosome (female)

XX-girl

XY-boy

Advantages of sexed semen

1)90% chance of producing a heifer calf being born

2) reduces the number of male dairy calves being born

3) can reduce the risk of calving difficulties in maiden heifers, since heifer calf’s are smaller than bull calves

Disadvantages of sexed semen

1) small chance that a male calf will be produced

2) sexed semen is more expensive than conventional,non sexed semen

3) sexed semen has fewer sperm per straw than non sexed semen straws (lower conception rates)

Methods of fertilisation 3 stock bull

•heifers can be difficult to detect when in heat

•some farmers keep a stock bull on their farm for breeding purposes

•a bull will detect when a cow is in or coming into heat

•when a cow/heifer is in heat she will stand allowing the bull to mount her

•bull will ejaculate and deposit semen in the vagina

•if a cow is coming into heat but not in standing heat she will move away and not allow bull to mount her

Disadvantages of stock bull

1) bulls are aggressive and can be dangerous

2) bulls are expensive to keep and require additional fencing

3) stock bull must be changed on a regular basis to prevent inbreeding within the herd

4)bulls can interfere with the breeding system on a farm eg by serving heifers

What is an embryo transplantation (E.T)

-used to produce large numbers of genetically superior animals bracket (not a natural method)

-this involves splitting apart cells from a developing animal embryo before they become specialised

-The identical embryos are then implanted into the uterus of host mothers

Day 1 e.t

> both the donor and recipient ewe are sponge with progesterone hormone impregnated sponges

>Both reproductive cycles of the donor and recipient ewe are synchronised

Day 10 e.t

>hormone injections are given to donor you to increase number of eggs released during ovulation super ovulation

Day 12 e.t

> Sponges removed from donor and recipient ewe

Day 13 e.t

>Heat detection is carried out on both ewes

>Teaser ram identifies ewe in heat

>Ewe comes into heat 48 hours after sponges are removed

Day 14 e.t

>Donor ewe is artificially inseminated using a laparoscope

>Fresh semen requires one insemination

>Frozen semen requires two inseminations

Day 20 e.t

>Embryos are flushed from donor ewe(superior genetics)

>Embryos are collected graded and transferred to recipient by inserting two into the horns of the uterus

>Donor ewe given injection to come back in heat four days later and is naturally serviced by ram

Advantages of embryo transplantation

1) this technique could be used to make many copies of cows that have a high milk yield(dairy)

2) it would produce a herd of cows much faster than if the original cow was used for breeding in the normal way

Disadvantages of embryo transplantation

1)expensive, could be stressful for animals

2) people do not want this procedure to be used in humans