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Reproduction > Repro Endocrinology LA > Flashcards

Repro Endocrinology LA Flashcards

1
Q

How may oestrus/ovulation be induced in the anovulatory post-partum cow or seasonally anoestrus ewe biologically?

A

Sustained increase in LH pulse frequency

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2
Q

How may LH pulse frequency be affected?

A
  • environmental factors eg. seasonal, day length, pheremones
  • physiological factors eg. post partum, lactation, pre-pubertal
  • pathological factors eg. uterine disease/endotoxins
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3
Q

What hormones has a negative feedback effect on pulsatile LH?

A

Oestradiol E2

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4
Q

What may be given artificially to impact LH pulse frequency?

A

GnRH in a pulsatile manner (2 hourly)

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5
Q

What should first be checked in an anovulatroy anoestrus/acyclical cow? What are the first steps in Tx?

A
  • true anoestrus not just a case of inefficient oestrus detection
  • correct underlying factors fisrt eg. negative energy balance, suckling/maternal bond, diseases eg. lameness, uterine infection
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6
Q

What hormonal based treatment of anovulatory anoestrus/acyclycity in cows can be implemented once underlying factors have been corrected?

A
  • PRID or CIDR for 12d

+- 500 iu eCG on day of removal

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7
Q

What repro hormone based Tx can be used to induce oestrus/ovulation in seasonally anoestrus ewes?

A
  • P4 sponge on day 0
  • Remove P4 sponge on day 12
  • PMSG/eCG injection 500 iu at
  • > freq LH pulses ^
  • add rams 24 hours later
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8
Q

What alternative Tx may be used to treat anoestrus ewes? Why is this not common? How else can this system be manipulated?

A
  • manipulation of photoperiod [difficult practically] 16h dark: 8h light
  • melatonin implants -> ear can also be used
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9
Q

Give egs of melatonin implants

A

Regulin

Melovine

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10
Q

What is the ram effect?

A
  • sound, sight and smell, perception of male by females
    (may be visual/physical contact, may be pheromones)
  • potential endocrine mechanism
    -> ewes ovulating 3-4d later
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11
Q

What is important to do before addition of any hormonal treatment in sheep?

A

P4 priming with sponge for 12d

- otherwise CL likely to be defective

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12
Q

How is puberty induced in gilts? What else is this indicated for?

A

> PG600 IM - combination of PMSG+hCG

  • to induce puberty given at 100kg BW or 6-7months
  • prevention of delayed puberty given at 8mo
  • prevention of anoestrus if given on day of weaning
  • Tx of anoestrus at d8-10 post weaning
  • prevention of anoestrus due to seasonal influence on day of weaning
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13
Q

How does Tx with PMSG/eCG differ in mechanism of action to giving GnRH?

A
  • no increase in endogenous FSH/LH as PMSG/eCG/hCG mimic the action of LH/FSH themselves
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14
Q

What are the advantages of synchronising oestrus in dairy cows?

A
  • avoid oestrus detection
  • fixed time AI
  • ^ preg rates
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15
Q

How is synchronisation of oestrus achieved in dairy cattle?

A

> control of luteal phase and/follicular growth

  • PGF2a -> CL lysis and shortening of luteal phase
  • Ovsynch - follicular wave synchrony (using GnRH) + PGF2a
  • Follicular wave synchrony with exogenous P4 (PRID/CIDR) + PGF2a to extend luteal phase??!! LOOKO UP
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16
Q

What causes luteolysis in the cow?

A
  • PGF2a synthesis by uterine endometrium released into uterine vein
  • diffuses into uterine artery (counter-current exchange)
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17
Q

Which hormone is high in the luteal phase?

A

Progesterone

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18
Q

How does PGF2a function? What is its ultimate effect? Is it reliable?

A
  • rapid decline of P4 due to CL lysis
  • oestrus 3-5 (range 2-7) days later
  • single injection not sufficient to synchronise whole herd as dependant on responsive CL presence.
  • heat detection still necessary if single injection given
  • pregnancy rates acceptable
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19
Q

How long is the cows oestrus cycle?

A

18-24 (21) d

20
Q

What are potential reasons for poor synchrony when using PGF2a?

A

> failure of luteolysis
- non-responsive CL, luteolytic from d6 of oestrus cycle (Tx too early in luteal phase)
- incorrect injection technique
timing dependent on follicular wave stage
- late wave takes v time -> ovulation from time of injection cf. early follicular phase

21
Q

How may injection of PGF2a techniques be improved to overcome synchrony problems?

A
  • Dx CL, inject and observe
  • 2 doses, 11 days apart to ensure responsive CL presence
    + fixed time AI [2+2 or 2+1 method]
22
Q

What are the 2+2 and 2+1 methods?

A

> 2+1: 2 doses of PGF2a + fixed time AI @ 72 and 96hrs

> 2+2: 2 doses of PGF2a + fixed time AI @ 84hrs

23
Q

What is ovsynch?

A

> follicle wave synchrony with GnRH + PGF2a

  • GnRH on d0 [if dom follicle present -> ovulation, if immature -> attrition], PGF2a on d7 [-> luteolysis]
  • GnRH again on d9 [induce LH surge and ovulation]
  • AI on d10
24
Q

What else may be used in lieu of GnRH for ovsynch?

A

P4 (PRID/CIDR) fro 8d pre PHF administration

25
Q

How may establishment of pregnancy be affected?

A
  • controlled by P4 (uterine secretions and endometrial structures)
  • compromised by insufficient rise post-ovulation (result of a defective CL)
  • ruminants: IFNt
  • pigs: oestrogens
26
Q

How may pregnancy be detected in the dairy cow? Problems with this?

A

P4 in the milk

- cannot differentiate between cyclic rise and pregnancy rise in the first 2 weeks after insemination

27
Q

Is P4 supplementation effective to improve pregnancy rates?

A
  • usually is effective
  • variable effectiveness depending on when P4 started
  • best when started <6d after AI (?)
28
Q

When is P4 supplementation most effective?

A
  • herds with low pregnancy rates
29
Q

What can be given as an alternative to P4 supplementation?

A
  • GnRH day 11 after AI (cows)

- GnRH day 9 after mating (sheep)

30
Q

What is COD and why does it occour?

A

> cystic ovarian disease

  • result of defect in ovulatory mechanism due to failure of pre-ovulatory LH surge
  • contributing factors = stress, v oestradiol, v hypothalamic sensitivity to oestradiol, uterine infection, NEB
31
Q

What is NEB?

A

Negatvie energy balance

32
Q

What is the Tx of LUTEAL cysts?

A

PG

- in heat after 3-4d

33
Q

What is the Tx of FOLLICULAR cysts?

A

NOT manual rupture!
- GnRH or hCG
- luteinises cyst or other follicles
[may secrete E2]

34
Q

What is the Tx of pyometra?

A

PGF2a (pyometra due to persistent CL)

35
Q

What is the Tx of pseudopregnancy in goats?

A

PGF2a (pseudopregnancy due to persisnt CL)

36
Q

What are the objectives of induced parturition?

A
  • synchronise calving with seasonal grazing
  • ensure calving coincides with availability of labour
  • therapeutic termination of pregnancies for various clinical reasons
37
Q

How is parturition initiated in the cow, sheep, goat and sow?

A
  • foetus initiates by stopping P4 production by CL or placenta
  • foetal PA axis determines timing of onset of parturition - cortisol production in foetal adrenal
  • > ^ oestrogen:progesterone ratio
38
Q

how does cortisol affect onset of parturition differently in goat, cow and sow cf. sheep

A

> goat, cow and sow
- cortisol -> aromatising enzymes (placenta)
- DHA (from foetal adrenal) converted to oestrogens in placenta
-> ^PGF2a
- CL regression, v P4 and ^ E2
Sheep
- cortisol affects multiple enzymes in Progesterone -> oestrogen pathway itself
-> Prostaglandins -> cervical softening, ^ myometrial contractions

39
Q

What 2 general ways may ovulation rate increase s be achieved?

A
  • ^ follicular recruitment

- v atresia

40
Q

What does ^ FSH case?

A

^ follicle recruitment

41
Q

How may superovulation be achieved?

A

> Giving FSH analiogues

  • recombinant FSH
  • pFSH
  • oFSH
  • eCG (PMSG)
  • purified porcine pituitary extract (PPPE)
42
Q

What is flushing and what does it cause?

A
  • ^ plane of nutiriton before mating
  • ^ energy intake LOWERS oestradiol concentration and promotion of FSH
  • > recruitment of follicles
43
Q

Which 2 hormones may be controlled immunologically?

A
  • Androstendione

- GnRH

44
Q

How is immunisation against androstenedione effective? Give examples of these products.

A
  • removed neg feedback on hypothalamus and pituitary -> ^FSH -> ^ follicles -> ^ ovulation rate in sheep
  • commercial product (Fecundin) single injection
  • androvax plus
  • ovastim
45
Q

How is immunisation against GnRH effective? Give examples of these products.

A
  • inhibits production of gonadotrophins and gonadal steroids
  • v testicular size and function
  • controls aggression and v male-associated odours
  • eg. vaxstrate (cattle)
  • equity (horses)
  • gonacon (white-tailed deer)
  • IMPROVAC (control of boar taint)
  • spayvac (multiple spp. including wild animals)

Reproduction (30 decks)

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