Applied reproductive endocrinology in LA Flashcards
How can you intervene to affect frequency of LH? 2
Environment/external signals: visual/olfactory
Internal signals
Why might you get anoestrous? 4
season
lactation
postpartum
pre-pubertal
What effect does E2 have?
negative feedback on pulsatile LH
How do you treat anovulatory anoestrous/acyclicity in cows?
Make sure it is ‘true’ anoestrous
Correct underlying factors first (NEB, maternal bond, disease)
PRID/CIDR for 12 days OR PRID/CIDR for 12 days + 500iu eCG on day of removal
How do you treat anovulatory anoestrous/acyclicity in cows?
P4 sponge + PMSG/eCG (500 iu) on day of P4 sponge removal
How can photoperiod be manipulated (ewes)?
Melatonin implants: Regulin or Melovine. Placed under skin of ear. Breed 30-60 days later.
16 hours darkness and 8 hours light (less practical)
What are the pre-conditions to the ram effect? 2
Effect?
- Isolation (sound, sight, smell, 4 weeks)
- Preception of male by females (visual, physical, pheromones)
RESULT: increased LH pulse frequency
What is the luteal function in GnRH-treated seasonally anoestrous ewe with or without P4 priming?
2/3 animals have a defective CL if not primed.
How can you induce puberty in gilts?
PG600 (PMSG + hCG) IM
No increase in FSH or LH by PMSG/eCG or hCG.
What can be controlled to synchronise oestrous? 2
control of luteal phase and/or follicular growth
Outline process of luteolysis in the cow.
P4 (CL) stimulates production of uterine PGF2a after d15 in cow –> PGF2a synthesis by uterine endometrium is released into uterine vein –> delivered back t ovary where it causes lysis of the CL
How many follicles are there on a cow’s ovary at any one time?
usually 1 dominant, most follicles are atretic though
How can you synchronise oestrous/ovulation?
PGF2a - control/shorten luteal phase
OVSYNCH: follicle wave synchrony + PGF2a, follicle wave synchrony with GnRH + control (shortening of luteal phase)
EXOGENOUS PROGESTERONE (PRID/CIDR) and PGF2a: follucle wave synchrony with P4 and control (extend) luteal phase
When does P4 decline after giving PGF2a?
Rapid decline of P4 and oestrous 3-5 (range 2-7) days later.
Synchrony not sufficient to avoid heat detection following single injection.
Pregnancy rates acceptable
What might be reasons for poor synchrony with PGF2a?
LUTEOLYSIS FAILURE:
non-responsive CL - luteolytic from day 6 of oestrous cycle (i.e. treatment too early in luteal phase)
incorrect injection technique
TIMING DEPENDENT ON FOLLICULAR WAVE STAGE
How can PGF2a problems be overcome?
Diagnose CL, inject, observe
OR
2 doses PGF2a, 11 days apart to ensure responsive CL is present + fixed time AI [either 2 doses + FTAI at 72 and 96 hours (2+2 method) OR 2 doses + FTAI at 85 hours (2+1 method)
Outline the ovsynch programme
GnRH - day 0 - synchronise new wave emergence
day 7 - PGF - cause luteolysis
day 9 - GnRH - control time of ovulation (by controlling LH surge in all animals)
day 10 - AI
What signal from the foetus maintains pregnancy in a.) ruminants b.) pigs?
Ruminants = IFNt Pigs = oestrogens
For how long after insemmination is it hard to differentiate between pregnant and cycling by P4 levels?
Days 0-6 after insemmination, after that it is easier to tell if pregnant or cyclic
When should P4 be supplemented during pregnancy?
Within first 6 days (i.e. first 6 days after insemmination)
How do you treat luteal deficiency/ poor maternal recognition of pregnancy?
P4 supplementation
OR
GnRH day 11 (cows) or 9 (ewes)
Why does COD occur?
Contributing factors?
defect in the ovulatory mechanism due to failure of the pre-ovulatory LH surge.
Contributing factors: stress lower oestradiol concentrations lower hypothalamic sensitivity to oestradiol uterine infection NEB
How to treat cysts:
LUTEAL
FOLLICULAR
OTHER
LUTEAL - PGF2a - in heat after 3-4 days?
FOLLICULAR - not manual rupture, GnRH or hCG - luteinises cyst or other follicles?
OTHERS: pyometra (persistent CL), pseudopregnancy in goats (persistent CL)> Treatment of both is with PGF2a
What initiates parturition in cows, sheep, goats and sows?
Foetus (all 4 species)
What does increased PGF2a at parturition cause?
CL regression
cervical softening
increased myometrial contraction
Which 3 enzymes does foetal cortisol raise in the mother?
17a hydroxylase (P4 –> 17a- hydroxyprogesterone)
C17-20 lyase (17a- hydroxyprogesterone –> androstenodione)
aromatase (androstenedione –> oestrogens)
How can you increase ovulation rate? 2
Increase in follicular recruitment
OR
decrease in atresia
What can you use to superovulate the donor?
recombinant FSH pFSH oFSH eCG (PMSG) Porcine pituitary extract (purified)
BUT there is variability in the superovulatory response (variation in ovulatory rate and recovery of viable embryos)
What does flushing do?
Increases follicular recruitment since high energy intake lowers oestradiol concentrations and promotes FSH release
How can you immunologically control reproduction? 2
immunisation against androstenedione
immunisation against GnRG
Why immunise against androstenedione?
Examples? 3
removes negative feedback on hypothalamus and pituitary
EXAMPLES:
A commercial product (Fecundin, Glaxo) uses a dextran adjuvant. Single injection. Increases ovulation rate in ewe.
Androvax Plus (Intervet)
Ovastim (Virbac)
What does immunising against GnRH do?
inhibits production of gonadotrophins and gonadal steroids
reduces testicular size and function
practised to control aggression and to reduce male-associated odours
What are examples of vaccines against GnRH? 3
Vaxstrate - cattle
Equity - horses (Pfizer)
IMPROVAC - controls Boar Taint
SpayVac - different species including wild animals
