Pharmacological Manipulation in Females Flashcards
When Would we Want to Pharmalogically Control Female Reproduction?
- Stimulation of the HPO axis
- Control of oestrus / ovulation
- Resolution of ovarian pathology
- Treatment of pseudopregnancy / termination of pregnancy
- Parturition and lactation
HPO Axis General Principles
- Hypothalmaus produces GnRH
- GnRH acts on anterior pituitary and stimulates production of LH and FSH
- FSH causes maturation of follicles, acts on granulosa cells
- Granulosa cells convert androgens to oestradiol
- Inhibin is produced by granulosa inhibits secretion of FSH
- Follicles become dependent on LH due to inhibin production
- LH surge is stimulated by high levels of oestradiol when it reaches positive feedback threshold
- LH stimulates ovulation of dominant follicle
- Ovulation of dominant follicle results in corpus luteum
- CL produces progesterone which has -ve feedback effect on hypothalamus and suppresses GnRH
- CL also produces oxytocin which binds to OXTR in endometrium
- Endometrium secretes PGF2a which lyses CL
Control of oestrus/ovulation
- Synchronisation of a group of animals
- Induction of ovulation
- Hasten return of cyclicity
○ E.g. after parturition, season, lactation - Prevent breeding (suppression)
How can we control oestrus/ovulation?
- Influencing photoperiod or its control
- Mimicking release of gonadotrophins for stimulatory or down-regulation purposes
- Lengthening or mimicking the luteal phase
- Blocking progesterone
- Shortening the luteal phase (PGF or Prolactin inhibitor)
Control of oestrus in farm animals
To INCREASE reproductive efficiency
Control of oestrus in sheep
○ Stimulate onset of cyclicity in early breeding season
Melatonin implant
Progestogen sponges for ~14 days in combination with eCG/GnRH
Ram effect
○ Synchronisation of breeding for management purposes
Control of oestrus in pigs
○ Synchronisation of a group of sows or gilts
Enables batch farrowing to occur
○ Progestogen (oral) for 14-18 days with or without eCG just before P4 removal
○ Limited hormonal use after weaning
○ Unable to use two doses of PGF
Because CL only responds after day 11
Control of Oestrus in Cattle
○ Aid oestrus detection / management of mating
Oestrus in cattle is short
Signs can be subtle
○ Multiple different protocols exist e.g.
○ OvSynch (with or without P4)
○ Progestogen plus PGF
○ Two doses of PGF ~12 days apart
○ May with fixed-time AI
Hormonal Protocols in Cattle
- Progesterone + PGF2a
- OvSynch
- OvSynch with Progesterone
Progesterone + PGF2a
Day 0 - Insert PRID to increase progesterone for a week
Day 7 - Give PGF2a to lyse any CL present
Rapid fall in progesterone will drive animal into follicular phase and into oestrus 2-3 days later
OvSynch
Day 0 - Give GnRH to induce ovulation of dominant follicle
Day 7 - Give PGF2a to lyse CL
Day 9 - Give GnRH to induce ovulation of dominant follicle
Use PRID in combination when with Heifers to drive animal into follicular phase
OvSynch
Day 0 - Give GnRH to induce ovulation of dominant follicle
Day 7 - Give PGF2a to lyse CL
Day 9 - Give GnRH to induce ovulation of dominant follicle
Use PRID in combination when with Heifers to drive animal into follicular phase
Control of Oestrus in companion animals
May be to SUPPRESS oestrus
Control of Oestrus in horses
○ Suppression of oestrus to enable training/performance
○ Give Progestogen at onset signs of proestrus for 10-15 days
Supresses HPT axis and therefore oestrus
○ May want to stimulate onset of cyclicity in early breeding season
Daylight
Oral progestogen for ~10 days once started cyclicity again
○ To manage AI/mating
Progestogen
PGF when active CL present
Hasten ovulation with hCG/GnRH
Control of Oestrus in Dogs
○ Prevention of oestrus
○ Suppression of oestrus
Progestogen depots for 6+ months (increased risk of pyometra if started in pro-oestrus or oestrus
GnRH agonist implant (takes time to act)
Testosterone in Greyhounds
○ Induction of oestrus (delayed puberty / prolonged lactational anoestrus)
Prolactin inhibitors for 2-5 weeks
GnRH agonist implant
hCG to induce ovulation
