Applied reproductive Endocrinology in Large Animals

Question 1

Reinstating reproductive activity in normal healthy animals

Answer 1

induce ovulation/oestrus in anovulatory post-partum cow
induce ovulation/oestrus in seasonally anoestrus ewe
induce puberty in pre-pubertal gilts
SUSTAINED INC IN LH PULSE FREQUENCY

Question 2

sustained increase in LH pulse frequency - physiological

Answer 2

seasonal
lactational
postpartum or pre-pubertal anoestrus

Question 3

sustained increase in LH pulse frequency - pathological

Answer 3

uterine disease/endotoxins

Question 4

sustained increase in LH pulse frequency

Answer 4

increase in E2 negative feedback effect on pulsatile LH

Question 5

treatment of anovulatory anoestrus/acylicity in the cow

Answer 5

make sure that its true anoestrus + not poor detection
correct the underlying factors 1st
PRID or CIDR for 12 days
PRID or CIDR for 12 days + 500 iu eCG on day of removal

Question 6

PRID

Answer 6

progesterone releasing intravaginal device

Question 7

CIDR

Answer 7

controlled internal drug release

Question 8

ram/boar effect

Answer 8

pre-conditions:sound, sight, smells, visual/physical contact

Question 9

GnRh treated ewe luteal function with P4 priming

Answer 9

priming with single P4 injection greatly increases luteal function

Question 10

induction of puberty in gilts

Answer 10

treat gilts with PG600 (PMSG [same os PCG] + hCG)

Question 11

increasing number of gametes

Answer 11

increase in follicular development

decrease in atresia of follicles

Question 12

superovulation of donor

Answer 12

recombinant FSH
pFSH
oFSH
eCG (PMSG)
porcine pituitary extract

Question 13

variability in superovulatory response

Answer 13

response is very variable even within same breed and management techniques

Question 14

manipulation of nutrition

Answer 14

increases follicular recruitment
flushing - rising plane of nutrition before mating
mechanism - high energy intake lowers oestradiol conc + promotes FSH release

Question 15

synchronisation of oestrus

Answer 15

controlled breeding without oestrus detection - fixed time AI, high pregnancy rates
control of luteal phase and/or follicular growth

Question 16

luteolysis in the cow

Answer 16

prostaglandin F2a (PGF2a) controls
prostaglandin synthesis by uterine endometrium released into uterine vein
progesterone from CL stimulates production of uterine PGF2a after day 15 in cow
PGF2a picked up by ovarian artery + taken back to ovary where it causes CL lysis

Question 17

synchronisation of oestrus/ovulation

Answer 17

PGF2a - control luteal phase
ovsynch - follicle wave scnchrony + PGF2a
exogenous progesterone with PGF2a, follicle wave synchrony with P4 + control luteal phase

Question 18

PGF2a - shortened luteal phase

Answer 18

rapid decline of progesterone + oestrus 3-5 days later
synchrony not sufficient to avoid heat detection following single injection
pregnancy rates acceptable

Question 19

PGF2a - possble reasons for poor synchrony

Answer 19

failure of luteolysis - non-responsive CL, incorrect injection technique
timing dependant on follicular wave stage

Question 20

PGF2a - methods to overcome problems

Answer 20

diagnose Cl, inject + observe

or 2 doses, 11 days apart to ensure responsive CL presence + fixed time AI

Question 21

ovsynch - follicle wave synchrony with GnRH + PGF2a

Answer 21

GnRH day 0 - synchronise new wave start
PGF2a day 7 - cause luteolysis
GnRH day 9 - control time of ovulation

Question 22

ovsynch - follicle wave synchrony with P4 + PGF2a

Answer 22

PRID used for 8 days
PGF2a given on day of removal of PRID
drop in P4 causes synch in ovulation

Question 23

maternal recognition of Pregnancy

Answer 23

establish pregnancy - communication between mother + embryo, controlled by P4, compromised by insufficient post-ovulatory rise in P4
ruminants - interferon tau
pigs - oestrogens

Question 24

luteal deficiency/poor maternal recognition of pregnancy

Answer 24

progesterone supplementation
GnRH day 11 (cow), day 9 (ewe)
works best in herd with low pregnancy rates

Question 25

onset of parturition - cow, goat, sow

Answer 25

foetus initiates
foetus must stop progesterone
foetal pituitary-adrenal axis determines timing of onset of parturition
as foetus grows in small space - stress
stress causes rise in foetal ACTH which causes increase in cortisol
rise in cortisol causes increased oestrogen:progesterone ratio

Question 26

immunisation against androstenedione

Answer 26

remove -ve feedback on hypothalamus + pituitary
commercial product uses a dextran adjuvant + increases ovulation rate in ewe
androvax plus
ovastim

Question 27

immunisation against GnRH

Answer 27

inhibits production of gonadotrophins + gonadal steroids
reduces testicular size + function
practised to control agression

Question 28

cystic ovarian disease (COD)

Answer 28

occurs as result of defect in ovulatory mechanism due to failure of pre-ovulatory LH surge
causes - stress, low oestradiol conc, low hypothalamic sensitivity to oestradiol, uterine infection + -ve energy balance