Reproductive Endocrinology in Large Animals

Question 1

Outline the aims of manipulating reproductive endocrinology in large animals…

Answer 1

1. Reinstating reproductive activity in healthy animals
2. Induction of puberty
3. Synchronisation of oestrus
4. Enhancement of embryo survival
5. Treatment of reproductive disease
6. Control of parturition
7. Increased the number of gametes
8. Immunological control of reproduction

Question 2

What hormonal action is necessary to reinstate reproductive activity in healthy adult animals?

Answer 2

Sustained increase in LH pulse frequency

Question 3

Outline the methods available for achieving a sustained increase in LH pulse frequentcy

Answer 3

Continuous infusion of GnRH
PMSG/eCG injection @ P4 sponge removal
Melatonin implants
Ram effects

Question 4

What may be given to gilts to induce puberty?

Answer 4

PG600 (PMSG and eCG) @ 6-7months or 100KG BW

Question 5

Outline the relationship between progesterone levels and LH pulse frequency

Answer 5

Low progesterone, high LH pulse frequency

Question 6

Outline how progesterone can be used to stimulate oestrus…

Answer 6

Give then remove (mimic luteal phase)

Question 7

Describe the levels of natural progesterone at anoestrus…

Answer 7

None

Question 8

What is a PRID?

Answer 8

Progesterone-releasing internal device

Question 9

What is CIDR?

Answer 9

Controlled internal drug release

Question 10

How is prostaglandin F2-alpha used in synchronisation of oestrus?

Answer 10

Control (shortening) of luteal phase

Question 11

How is Ovsynch used in synchonisation of oestrus?

Answer 11

Follicle wave synchrony and PGF2-alpha
Follicular wave synchrony with GnRH
Control (shortening) of luteal phase with PGF2-alpha

Question 12

Outline how PRID/CIDR are used in synchronisation of oestrus…

Answer 12

Exogenous progesterone and PGF2-alpha
Follicle wave synchrony with P4
Control (shortening) of luteal phase with PGF2-alpha

Question 13

How long are progesterone sponges used for prior to removal?

Answer 13

10-12 days

Question 14

Outline the possible reasons for poor synchrony when using PGF2-alpha…

Answer 14

Treatment too early in luteal phase (CL not responsive)
Incorrect injection technique
Timing dependent of follicular wave stage

Question 15

How might PGF1-alpha injections be timed to ensure the presence of a responsive CL?

Answer 15

2 injections 11 days apart

Question 16

How long may melatonin implants take to induce effects?

Answer 16

35-70 days

Question 17

When is natural melatonin secreted?

Answer 17

Dark period

Question 18

Outline how melatonin affects short day breeders…

Answer 18

Melatonin secreted from pineal gland in dark period (16hr)
More frequent GnRH pulses
LH release causes breeding activity

Question 19

Outline the ram efect…

Answer 19

Separate rams from ewes for >4weeks
Prime ewes with progesterone 3-5 days before reintroduction (inj/spong)
Ovulation 4-5 days after reintroduction

Question 20

Why are ewes primed with progesterone when synchronising oestrus using the ram effect?

Answer 20

To ensure normal, functional CL and maintenance of pregnancy

Question 21

Other than progesterone, which hormone is needed for estalishments of pregnancy in ruminanats?

Answer 21

Interferon tau

Question 22

Other than progesterone, which hormone is needed for establishment of pregnancy in pigs?

Answer 22

Oestrogens

Question 23

From where is natural PGF2-alpha secreted?

Answer 23

Endometrium

Question 24

How does PGF2-alpha reach the ovary?

Answer 24

Taken from endometrium to the ovarian artery via the uterine vein (countercurrent system)

Question 25

Outline the available methods for treatment of luteal deficiency/poor maternal recognition of pregnancy...

Answer 25

Progesterone supplementation GnRH Cows - day 11 Ewes - day 9

Question 26

Why might you inject an animal with PGF2-alpha 1 day before removing a PRID?

Answer 26

Allows dominant follicle to ovulate

Question 27

When should progesterone supplementation be given for treatment of luteal deficiency?

Answer 27

<6 days after insemination

Question 28

Outline the effect of continued follicular development on establishment of pregnancy...

Answer 28

Causes high oestrogen leading to poor establishment of pregnancy

Question 29

How might you treat continued follicular development following establishment of pregnancy?

Answer 29

Use GnRH to lyse remaining follicles

Question 30

What is secreted by follicular cysts?

Answer 30

Variable concentrations of oestrogens

Question 31

How can GnRH bolus injections be used to synchronise a herd's follicle development waves?

Answer 31

Heavy dose leads to LH surge Causes ovulation or luteolysis All animals begin new follicle development wave

Question 32

Why does cystic ovarian disease occur?

Answer 32

Result of a defect in the ovulatory mechanism due to the failure of the pre-ovulatory LH surger

Question 33

Outline the factors contributing to cystic ovarian disease...

Answer 33

``` Stress Low oestrodial concentration Low hypothalamic sens to oestrodial Uterine infection NEB ```

Question 34

Outline treatment of luteal cysts...

Answer 34

PGF2-alpha

Question 35

Outline treatment of follicular cysts...

Answer 35

GnRH or hCG

Question 36

Outline treatment of pyometra (persistent CL)

Answer 36

PGF2-alpha

Question 37

Outline treatment of pseudopregnancy in goats (persistent CL)

Answer 37

PGF2-alpha

Question 38

Outline the objectives of induced parturition...

Answer 38

To synchronise calving with grazing season To ensure that calving coincides with availability of labour For therapeutic termination of pregnancy

Question 39

Outline the onset of parturition in the cow/sheep/goat/sow

Answer 39

Initiated by foetus Growth in restricted space leads to foetal stress Stress leads to a rise in foetal ACTH, and consequently cortisol Rise in foetal cortisol leads to increase maternal oestrogen:progesterone ratio

Question 40

Outline the 2 methods for increasing ovulation rate...

Answer 40

Decrease atresia | Increase follicular recruitment

Question 41

Which agents can be used to induced super ovulation?

Answer 41

``` Recombinant FSH pFSH oFSH eCG Purified porcine pituitary extract ```

Question 42

What is flushing?

Answer 42

Rising plane of nutrition before mating to lower oestrogen and promote FSH release

Question 43

Outline the action of androstenedione...

Answer 43

Removes negative feedback on hypothalamus and pituitary

Question 44

Outline the purposes of immunisation against GnRH..

Answer 44

Inhibits production of gonadotrophins and gonadal steroids Reduces testicular size and function Control aggression Reduces male-associated odours