oestrus manipulation

Question 1

hypothalamus pituitary ovarian axis hormones

Answer 1

GnRH acts on
pituitary - FSH and LH acts on
Ovary - inhibin (stop other follicles becoming dominant) , oestradiol (behavioural level of oestrus)
- progesterone (from CL) , oxytocin
endometrium - PGF2Alpha induced luteoloysis to restart and produce new follicles

Question 2

what hormone spikes to cause ovulation

Answer 2

LH

Question 3

what happens when CL is still present but recruitment of follicles continues? (multiple follicular waves)

Answer 3

high level of progesterone causes negative feedback on hypothalamus - reduced LH and FSH.
follicles grow to certain point and regress or become static and do not grow any further.

Question 4

heat detection rate of dairy cows (oestrus detection)

Answer 4

60% heat detection rate

Question 5

oestrus behaviour in cows

Answer 5

• best way of detecting - standing to be mounted (10-12 hours in heat to be serviced)
  mount others
  chin pressing and licking
  sniffing
  increased walking, bellowing and general restlesness
  swelling of vulva and mucus discharge
  riding marks

Question 6

oestrus detection aids

Answer 6

tail paint/chalk - rubbed off when mounted
mount indicator - changes colour when mounted - white to red
activity monitors (pedometers)

Question 7

how do we know mare is in oestrus?

Answer 7

ovulate 24 hours before behavioural oestrus.
- follicle observation - ultrasound
>35mm - daily growth of 3-5mm
tear drop shaped <24hours to ovulation
becomes softer <6-12hours ovulation
follicle wall thickens 24h prior to ovulation
oedema

Question 8

difference between vaginal cytology of a bitch with anoestrus and pro-oestrus

Answer 8

round cells with really large nucleus - anoestrus
more triangular cells with tiny nucleus (cornified) - 7 days before she is in full oestrus and ready to be mated - pro-oestrus

Question 9

progesterone testing in bitch

Answer 9

increases to 5-10ng/ml at ovulation from <2ng/ml allow 48 hours for maturation then rises to 40/50 after ovulation

Question 10

reasons for manipulating oestrus

Answer 10

• poor oestrus detection
• synchronisation
• enable AI and ET
• trigger post partum resumption

Question 11

what hormone shortens the luteal phase?

Answer 11

PGF2A - get rid of CL and mimics

Question 12

what hormone is used to extend luteal phase?

Answer 12

progesterone

Question 13

what hormone is used to recruit and grow follicles?

Answer 13

GnRH or FSH
PMSG eCG

Question 14

what hormone is used to stimulate ovulation?

Answer 14

GnRH or LH
hCG

Question 15

what hormone will arrest the oestrus cycle?

Answer 15

Progesterone - negative feedback on hypothalamus - stops secreting GnRH

Question 16

give example of 10 day cycle of synchronising a heard and hormones used

Answer 16

day 0 - GnRH, synchronise new wave emergence
day 7 - PGF2A - cause luteolysis, gets rid of CL
day 9 - GnRH - control time of ovulation
day 10 - AI

Question 17

fixed time AI for heifers

Answer 17

2 doses of PGF2A 11 days apart
or
double AI @ 72 + 96h
or
single AI @ 84h

Question 18

how does PGF2A 2 doses work

Answer 18

1st = just to make sure everyone has a corpus luteum
heifer with CL - luteolysis, new follicle, ovulation and CL
2nd =
all have CL, luteolysis, new follicle, ovulation

Question 19

alternative for synchronisation >50days after calving

Answer 19

exogenous progesterone device - stops hypothalamus from producing GnRH

Question 20

problems of using progesterone sponge

Answer 20

• lower pregnancy rate
• higher ram: ewe required (1:10)
• risk of triplets and quads due recruiting multiple follicles due to too high a gonadotropin dose

Question 21

causes of anoestrus

Answer 21

• pregnancy
• lactation
• season
• negative energy balance
• stress
• pathology

Question 22

anoestrus management devices

Answer 22

progesterone devices:
PRID
CIDR
removal causes GnRH surge

Question 23

manipulation in pigs

Answer 23

PGF2A to synch 2nd oestrus in gilts
stimulates activity post farrowing in sows
PMSG and hCG combined to induce puberty in gilt