Assisted Reproductive Technologies Flashcards
What are the main assisted reproductive technologies?
- Artifical insemination
- Semen sorting
- Multiple ovulation & embryo transfer
- IV production of embryos
- Cloning
Name 4 ways hormones can be manipulated to control reproductive cycles
- Breeding season extension
- Oestrus synchronisation
- Multiple ovulation
- Hormonal treatments of infertility
How is oestrus synchronisation carried out?
- Injections of progesterone - inhibit oestrus by preventing release of GnRH, LH & FSH & ovulation
- Treatment must be long enough to allow CL to regress to obtain synchronisation
- Oestrus & ovulation are prevented until treatment is withdrawn
- Once withdrawn, the pulsed release of GnRH leads to LH/FSH release & oestrus in 2-6 days
What have progesterone injections been replaced with?
Synthetic progestins in the form of implants or topical applications
Give 4 management advantages to synchronising oestrus cycles
- Numbers of females can be brought into oestrus at the same time so can be ‘batched’
- Allows scheduling of handling tasks
- Reduces time spent on oestrus detection
- In some species, this allows the breeder to shift the breeding process (planning parturition so offspring ready form market at most profitable time)
Give 4 problems that can arise when synchronising oestrus in cattle
- Conception rates are about 15% below normal (can be improved by combining progestin and
oestrogen) - Treatment of undetected already pregnant animals can cause abortion
- Animals must be cycling and not in the post-partum anoestrus phase
- Heifers must be checked to ensure they have reached puberty
What can testosterone replacement therapy be used to treat?
- Hypogonadism
- Androgen deficiency
What is a negative result of testosterone replacement therapy?
Exogenous testosterone adversely spermatogenesis
How can injections with human chorionic gonadotropin aid in fertility?
- HCG stimulates leydig cell production of testosterone so helps to maintain or increase intratesticular level of testosterone
- In non ovulating females, can stimulate follicular development in ovaries, leading to ovulation
Give an example of a selective oestrogen receptor modulator
- Clomiphene
- Induces ovulation by inhibiting oestrogen receptors in hypothalamus, blocking negative feedback of oestrogen on gonadatropin release
- Hypothalamus perceives low levels of LH/FSH so trigger pituitary to produce more
- Can also be used on males to stimulate testosterone production
What is artificial insemination?
- Allows fertilisation with semen from specific individuals or strains from anywhere without transporting animals
- Can also be used in conservation of breeding programs
How is artificial insemination carried out?
- Semen collected from male
- Frozen in plastic tubes (straws)
- Mixed with solution containing glycerol or other cryoprotectants
Give 4 advantages of artificial insemination
- Allows insemination of a large number of females from a single mate
- Allows control of paternity of offspring
- Overcomes physical breeding difficulties in some species
- Avoids injury to valuable animals during natural mating
What is intrauterine insemination?
- Effectively AI
- Inserts semen sample into uterus just before ovulation
What is the goal with sexed semen?
- To produce a calf of a specific sex
