Repro Endocrinology LA

Question 1

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

Answer 1

Sustained increase in LH pulse frequency

Question 2

How may LH pulse frequency be affected?

Answer 2

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

Question 3

What hormones has a negative feedback effect on pulsatile LH?

Answer 3

Oestradiol E2

Question 4

What may be given artificially to impact LH pulse frequency?

Answer 4

GnRH in a pulsatile manner (2 hourly)

Question 5

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

Answer 5

• 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

Question 6

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

Answer 6

• PRID or CIDR for 12d

+- 500 iu eCG on day of removal

Question 7

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

Answer 7

• 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

Question 8

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

Answer 8

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

Question 9

Give egs of melatonin implants

Answer 9

Regulin

Melovine

Question 10

What is the ram effect?

Answer 10

• 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

Question 11

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

Answer 11

P4 priming with sponge for 12d

- otherwise CL likely to be defective

Question 12

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

Answer 12

> 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

Question 13

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

Answer 13

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

Question 14

What are the advantages of synchronising oestrus in dairy cows?

Answer 14

• avoid oestrus detection
• fixed time AI
• ^ preg rates

Question 15

How is synchronisation of oestrus achieved in dairy cattle?

Answer 15

> 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

Question 16

What causes luteolysis in the cow?

Answer 16

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

Question 17

Which hormone is high in the luteal phase?

Answer 17

Progesterone

Question 18

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

Answer 18

• 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

Question 19

How long is the cows oestrus cycle?

Answer 19

18-24 (21) d

Question 20

What are potential reasons for poor synchrony when using PGF2a?

Answer 20

> 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

Question 21

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

Answer 21

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

Question 22

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

Answer 22

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

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

Question 23

What is ovsynch?

Answer 23

> 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

Question 24

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

Answer 24

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

Question 25

How may establishment of pregnancy be affected?

Answer 25

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

Question 26

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

Answer 26

P4 in the milk | - cannot differentiate between cyclic rise and pregnancy rise in the first 2 weeks after insemination

Question 27

Is P4 supplementation effective to improve pregnancy rates?

Answer 27

- usually is effective - variable effectiveness depending on when P4 started - best when started <6d after AI (?)

Question 28

When is P4 supplementation most effective?

Answer 28

- herds with low pregnancy rates

Question 29

What can be given as an alternative to P4 supplementation?

Answer 29

- GnRH day 11 after AI (cows) | - GnRH day 9 after mating (sheep)

Question 30

What is COD and why does it occour?

Answer 30

> 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

Question 31

What is NEB?

Answer 31

Negatvie energy balance

Question 32

What is the Tx of LUTEAL cysts?

Answer 32

PG | - in heat after 3-4d

Question 33

What is the Tx of FOLLICULAR cysts?

Answer 33

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

Question 34

What is the Tx of pyometra?

Answer 34

PGF2a (pyometra due to persistent CL)

Question 35

What is the Tx of pseudopregnancy in goats?

Answer 35

PGF2a (pseudopregnancy due to persisnt CL)

Question 36

What are the objectives of induced parturition?

Answer 36

- synchronise calving with seasonal grazing - ensure calving coincides with availability of labour - therapeutic termination of pregnancies for various clinical reasons

Question 37

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

Answer 37

- 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

Question 38

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

Answer 38

> 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

Question 39

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

Answer 39

- ^ follicular recruitment | - v atresia

Question 40

What does ^ FSH case?

Answer 40

^ follicle recruitment

Question 41

How may superovulation be achieved?

Answer 41

> Giving FSH analiogues - recombinant FSH - pFSH - oFSH - eCG (PMSG) - purified porcine pituitary extract (PPPE)

Question 42

What is flushing and what does it cause?

Answer 42

- ^ plane of nutiriton before mating - ^ energy intake LOWERS oestradiol concentration and promotion of FSH - > recruitment of follicles

Question 43

Which 2 hormones may be controlled immunologically?

Answer 43

- Androstendione | - GnRH

Question 44

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

Answer 44

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

Question 45

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

Answer 45

- 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)