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Reproduction > Applied reproductive endocrinology in LA > Flashcards

Applied reproductive endocrinology in LA Flashcards

1
Q

How can you intervene to affect frequency of LH? 2

A

Environment/external signals: visual/olfactory

Internal signals

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2
Q

Why might you get anoestrous? 4

A

season
lactation
postpartum
pre-pubertal

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3
Q

What effect does E2 have?

A

negative feedback on pulsatile LH

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4
Q

How do you treat anovulatory anoestrous/acyclicity in cows?

A

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

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5
Q

How do you treat anovulatory anoestrous/acyclicity in cows?

A

P4 sponge + PMSG/eCG (500 iu) on day of P4 sponge removal

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6
Q

How can photoperiod be manipulated (ewes)?

A

Melatonin implants: Regulin or Melovine. Placed under skin of ear. Breed 30-60 days later.

16 hours darkness and 8 hours light (less practical)

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7
Q

What are the pre-conditions to the ram effect? 2

Effect?

A
  • Isolation (sound, sight, smell, 4 weeks)
  • Preception of male by females (visual, physical, pheromones)

RESULT: increased LH pulse frequency

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8
Q

What is the luteal function in GnRH-treated seasonally anoestrous ewe with or without P4 priming?

A

2/3 animals have a defective CL if not primed.

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9
Q

How can you induce puberty in gilts?

A

PG600 (PMSG + hCG) IM

No increase in FSH or LH by PMSG/eCG or hCG.

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10
Q

What can be controlled to synchronise oestrous? 2

A

control of luteal phase and/or follicular growth

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11
Q

Outline process of luteolysis in the cow.

A

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

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12
Q

How many follicles are there on a cow’s ovary at any one time?

A

usually 1 dominant, most follicles are atretic though

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13
Q

How can you synchronise oestrous/ovulation?

A

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

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14
Q

When does P4 decline after giving PGF2a?

A

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

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15
Q

What might be reasons for poor synchrony with PGF2a?

A

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

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16
Q

How can PGF2a problems be overcome?

A

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)

17
Q

Outline the ovsynch programme

A

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

18
Q

What signal from the foetus maintains pregnancy in a.) ruminants b.) pigs?

A 
Ruminants = IFNt
Pigs = oestrogens
19
Q

For how long after insemmination is it hard to differentiate between pregnant and cycling by P4 levels?

A

Days 0-6 after insemmination, after that it is easier to tell if pregnant or cyclic

20
Q

When should P4 be supplemented during pregnancy?

A

Within first 6 days (i.e. first 6 days after insemmination)

21
Q

How do you treat luteal deficiency/ poor maternal recognition of pregnancy?

A

P4 supplementation
OR
GnRH day 11 (cows) or 9 (ewes)

22
Q

Why does COD occur?

Contributing factors?

A

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
23
Q

How to treat cysts:
LUTEAL
FOLLICULAR
OTHER

A

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

24
Q

What initiates parturition in cows, sheep, goats and sows?

A

Foetus (all 4 species)

25
Q

What does increased PGF2a at parturition cause?

A

CL regression
cervical softening
increased myometrial contraction

26
Q

Which 3 enzymes does foetal cortisol raise in the mother?

A

17a hydroxylase (P4 –> 17a- hydroxyprogesterone)

C17-20 lyase (17a- hydroxyprogesterone –> androstenodione)

aromatase (androstenedione –> oestrogens)

27
Q

How can you increase ovulation rate? 2

A

Increase in follicular recruitment
OR
decrease in atresia

28
Q

What can you use to superovulate the donor?

A 
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)

29
Q

What does flushing do?

A

Increases follicular recruitment since high energy intake lowers oestradiol concentrations and promotes FSH release

30
Q

How can you immunologically control reproduction? 2

A

immunisation against androstenedione

immunisation against GnRG

31
Q

Why immunise against androstenedione?

Examples? 3

A

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)

32
Q

What does immunising against GnRH do?

A

inhibits production of gonadotrophins and gonadal steroids
reduces testicular size and function
practised to control aggression and to reduce male-associated odours

33
Q

What are examples of vaccines against GnRH? 3

A

Vaxstrate - cattle
Equity - horses (Pfizer)
IMPROVAC - controls Boar Taint
SpayVac - different species including wild animals

Reproduction (42 decks)

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