Reproductive Endocrinology in Large Animals Flashcards
Outline the aims of manipulating reproductive endocrinology in large animals…
- Reinstating reproductive activity in healthy animals
- Induction of puberty
- Synchronisation of oestrus
- Enhancement of embryo survival
- Treatment of reproductive disease
- Control of parturition
- Increased the number of gametes
- Immunological control of reproduction
What hormonal action is necessary to reinstate reproductive activity in healthy adult animals?
Sustained increase in LH pulse frequency
Outline the methods available for achieving a sustained increase in LH pulse frequentcy
Continuous infusion of GnRH
PMSG/eCG injection @ P4 sponge removal
Melatonin implants
Ram effects
What may be given to gilts to induce puberty?
PG600 (PMSG and eCG) @ 6-7months or 100KG BW
Outline the relationship between progesterone levels and LH pulse frequency
Low progesterone, high LH pulse frequency
Outline how progesterone can be used to stimulate oestrus…
Give then remove (mimic luteal phase)
Describe the levels of natural progesterone at anoestrus…
None
What is a PRID?
Progesterone-releasing internal device
What is CIDR?
Controlled internal drug release
How is prostaglandin F2-alpha used in synchronisation of oestrus?
Control (shortening) of luteal phase
How is Ovsynch used in synchonisation of oestrus?
Follicle wave synchrony and PGF2-alpha
Follicular wave synchrony with GnRH
Control (shortening) of luteal phase with PGF2-alpha
Outline how PRID/CIDR are used in synchronisation of oestrus…
Exogenous progesterone and PGF2-alpha
Follicle wave synchrony with P4
Control (shortening) of luteal phase with PGF2-alpha
How long are progesterone sponges used for prior to removal?
10-12 days
Outline the possible reasons for poor synchrony when using PGF2-alpha…
Treatment too early in luteal phase (CL not responsive)
Incorrect injection technique
Timing dependent of follicular wave stage
How might PGF1-alpha injections be timed to ensure the presence of a responsive CL?
2 injections 11 days apart
How long may melatonin implants take to induce effects?
35-70 days
When is natural melatonin secreted?
Dark period
Outline how melatonin affects short day breeders…
Melatonin secreted from pineal gland in dark period (16hr)
More frequent GnRH pulses
LH release causes breeding activity
Outline the ram efect…
Separate rams from ewes for >4weeks
Prime ewes with progesterone 3-5 days before reintroduction (inj/spong)
Ovulation 4-5 days after reintroduction
Why are ewes primed with progesterone when synchronising oestrus using the ram effect?
To ensure normal, functional CL and maintenance of pregnancy
Other than progesterone, which hormone is needed for estalishments of pregnancy in ruminanats?
Interferon tau
Other than progesterone, which hormone is needed for establishment of pregnancy in pigs?
Oestrogens
From where is natural PGF2-alpha secreted?
Endometrium
How does PGF2-alpha reach the ovary?
Taken from endometrium to the ovarian artery via the uterine vein (countercurrent system)
Outline the available methods for treatment of luteal deficiency/poor maternal recognition of pregnancy…
Progesterone supplementation
GnRH
Cows - day 11
Ewes - day 9
Why might you inject an animal with PGF2-alpha 1 day before removing a PRID?
Allows dominant follicle to ovulate
When should progesterone supplementation be given for treatment of luteal deficiency?
<6 days after insemination
Outline the effect of continued follicular development on establishment of pregnancy…
Causes high oestrogen leading to poor establishment of pregnancy
How might you treat continued follicular development following establishment of pregnancy?
Use GnRH to lyse remaining follicles
What is secreted by follicular cysts?
Variable concentrations of oestrogens
How can GnRH bolus injections be used to synchronise a herd’s follicle development waves?
Heavy dose leads to LH surge
Causes ovulation or luteolysis
All animals begin new follicle development wave
Why does cystic ovarian disease occur?
Result of a defect in the ovulatory mechanism due to the failure of the pre-ovulatory LH surger
Outline the factors contributing to cystic ovarian disease…
Stress Low oestrodial concentration Low hypothalamic sens to oestrodial Uterine infection NEB
Outline treatment of luteal cysts…
PGF2-alpha
Outline treatment of follicular cysts…
GnRH or hCG
Outline treatment of pyometra (persistent CL)
PGF2-alpha
Outline treatment of pseudopregnancy in goats (persistent CL)
PGF2-alpha
Outline the objectives of induced parturition…
To synchronise calving with grazing season
To ensure that calving coincides with availability of labour
For therapeutic termination of pregnancy
Outline the onset of parturition in the cow/sheep/goat/sow
Initiated by foetus
Growth in restricted space leads to foetal stress
Stress leads to a rise in foetal ACTH, and consequently cortisol
Rise in foetal cortisol leads to increase maternal oestrogen:progesterone ratio
Outline the 2 methods for increasing ovulation rate…
Decrease atresia
Increase follicular recruitment
Which agents can be used to induced super ovulation?
Recombinant FSH pFSH oFSH eCG Purified porcine pituitary extract
What is flushing?
Rising plane of nutrition before mating to lower oestrogen and promote FSH release
Outline the action of androstenedione…
Removes negative feedback on hypothalamus and pituitary
Outline the purposes of immunisation against GnRH..
Inhibits production of gonadotrophins and gonadal steroids
Reduces testicular size and function
Control aggression
Reduces male-associated odours
