The oestrus cycle

Question 1

Give examples of polyoestrus animals that cycle constantly throughout the year?

Answer 1

Cow, pig and rodent

Question 2

Give examples of seasonal oestrus cycle animals that cycle during a specific season?

Answer 2

Long day (spring, mare and deer)
Short day (autumn, ewe)

Question 3

Give and example of a monoestrus animal that has infrequent cycles independent of season?

Answer 3

Dogs.

Question 4

What are some of the methods used to manipulate seasonal breeders?

Answer 4

Artificial change to photoperiod i.e. put mares
& stallions under lights at Xmas.
Physical change to photoperiod i.e. “shuttle”
stallions travel from northern to southern hemispheres
biannually.

Question 5

What are the signs of oestrus in the female?

Answer 5

— Is receptive to the male (lordosis) &

— has high levels of oestrogens

Question 6

What are the signs of dioestrus in the female?

Answer 6

— rejects the male &

— has high levels of progesterone

Question 7

What are phases of the oestrus cycle?

Answer 7

Prooestrus* — phase immediately before
oestrus
Oestrus
Metoestrus* — succeeds oestrus, corpus
luteum forms
Dioestrus
*not obvious in all species

Question 8

What stage of the oestrus cycle is the bitch likely to be in during the follicular and luteolytic phase and which hormone governs this?

Answer 8

Pro-oestrus and oestrus.

Oestrogen.

Question 9

What stage of the oestrus cycle is the bitch likely to be in during the luteal phase and which hormone governs this?

Answer 9

Metoestrus and dioestrus

Progesterone

Question 10

What does FSH do?

Answer 10

Stimulates maturation of germ cells (all stages of gametes)

Question 11

What does LH do in the male and the female?

Answer 11

. luteinising hormone stimulates production & secretion of steroids:
— testosterone in testes
- oestrogen & progesterone in ovaries

Question 12

What are some oestrus detection methods used in cattle?

Answer 12

Kamars, pedometers, estrotect, GPS, Van Eerdenbergs scoring, Low plasma/milk progesterone, crystallisation patterns in the vaginal mucus, a fall in body temperature prior to oestrus, a reduction in vaginal pH
10 15 Days in relation to ovulation

Question 13

What factors can inhibit oestrus behaviour in cows?

Answer 13

— Hard, non-supportive floor is best
— Concrete reduces oestrous behaviour by up to 50%
especially when wet and slippery
— High environmental temperature
— Overcrowding
— Recent mixing / stress
— Lameness
- FEEDING
Think of poor observation first

Question 14

What can be used in cows to synchronise ovulation?

Answer 14

Ovsynch

Question 15

Signs of oestrus in the sow?

Answer 15

VuIva swollen and congested prior to oestrus
Seeks the boar
Stands firmly to be mounted (the
back pressure test (she won’t move
when you put pressure on her; very
reliable)

Question 16

Signs of oestrus in the mare?

Answer 16

Detection of a large follicle (>20mm) in absence of a CL)
(by palpation or ultrasound examination)
Demonstration of follicle size, follicle wall thickening, follicle softening on ultrasound examination

Question 17

How long does proestrus typically last in the bitch and what are the signs?

Answer 17

— Very long (classically 9 days)
— Bitch is attractive to the male but will not allow
mating
—Vulvalswelling
— Presence of a serosanguinous discharge
(bloody discharge from vulva)

Question 18

What are the signs of oestrus in the bitch and what is the average length?

Answer 18

. Oestrus: 9 days
— Standing to be mated
— Deviation of tail
— Discharge becomes paler in colour
— Reduction in vulvaloedema

Question 19

What is the most effective method of oestrus detection in the bitch?

Answer 19

Vaginal cytology

Should see anucleate epithelial cells during oestrus

Question 20

What kind of ovulators are cats?

Answer 20

Induced ovulators.
LH response to mating decreases with each day
of oestrus and follicles ultimately regress

Question 21

What are signs of oestrus in the queen?

Answer 21

. Increased vocalisation, rubbing and rolling
. Increased activity and will seek tom
. Possible slight mucoid vulval discharge

Question 22

What is an induced ovulator? And what species exhibit this?

Answer 22

— The presence of an antral follicle and increased oestrogen are still prerequisite for LH release and ovulation HOWEVER, copulation results in neuro-endocrine response resulting in LH release and then ovulation
- Examples: cat, rabbit, ferret, mink, camelids

Question 23

What are the series of hormonal events that lead to dominant follicle selection?

Answer 23

Oestradiol and inhibin increase causing FSH to drop and subordinate follicles to degenerate.

Question 24

What sequence of hormonal events initiates ovulation?

Answer 24

Non pregnant uterus secretes PGF2a, causing luteolysis, meaning progesterone drops, oestradiol is secreted from ovulatory follicle causing an LH surge and next ovulation.

Question 25

What does pseudopregnancy happen in the bitch?

Answer 25

She has no LP shift. Progesterone is produced throughout pregnancy by the ovary. Prolaction also maintains the CL.