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Control of Reproduction in the FEMALE (Suppression of oestrus (Stop…
Control of Reproduction in the FEMALE
Induction of oestrus.
Need to= establish normal pattern of gonadotrophins
Might: supply GnRH, FSH, LH/ ovarian steroids to stimulate normal patterns of release from Anterior Pituitary
Suppression of oestrus
Stop release of gonadotrophins
Prog=
negative feedback on hypothalamus and pituitary
Androgens=
inhibit gonadotrophin release
Synchronisation of oestrus
Control follicular waves so oestrus and ovulation happen at similar times in all animals
Control of Oestrus cycle
Requires a controlled start to one follicular wave
i) Start a new wave by removing the dominant follicle
(new wave in 1-5d)
GnRH=
causes atresia/ luteinisation of existing follicles
Given After selection of DF=
ovulation and new wave 1-2d
Given Before selection of DF=
no effect, DF formed in 3.6d
Aspiration of follicle
(physical)
Oestrogens=
regression of follicle (not in food producing animals)
ii) Remove luteal influence
, removes prog inhibition on the pituitary,
allows a new wave
Get rid of progesterone by
causing luteolysis
OR
Prolong prog effect
- then stop! (too long= ova hangs, ages too much for good fertility
PG= PGF2alpha
(destruction of CL- stops blood flow)
Oestradiol=
if early in cycle prevents CL formation, later: induction of oxytocin and release of endogenous PG
(NOT IN food producing animals)
Regimes
Combination
of drugs/ techniques to synchronise start of new wave and end a luteal phase
Superovulation
Enhance n# of follicles recruited
Enhance n# of follicles which go on to become DF and ovulate
Induction of abortion
Induction of parturition
Requires good knowledge of normal events in parturition, feed into using exogenous drugs
Reproductive technology- AI, ET, cloning etc
Follicular dynamics
sheep + cattle (polyestrous sp.)=
develop in waves, repeated every 8-12d during each oestrous cycle (2-3 waves per cycle)
Hormone Profile
