Oestrus vs menstrual cycle

Question 1

What are the only group of animals that menstruate?

Answer 1

Primates

Question 2

In domestic animals what is used as the reference point for the first day of the cycle?

Answer 2

First day of oestrus

Question 3

What is meant by oestrus?

Answer 3

• In heat = sexually receptive to the male
• behavioural signs
• ready to be mated by a male

Question 4

Which hormone drives the oestrous period?

Answer 4

High levels of oestrogen which cause an LH surge

Question 5

What follows ovulation?

Answer 5

Development of the corpus luteum which secretes progesterone

Question 6

How does day 0 of the menstrual and oestrus cycles differ?

Answer 6

Menstrual = low oestrogen, bleeding
Oestrus = high oestrogen, animal sexually receptive, no bleeding

Question 7

How long are menstrual and oestrus cycles?

Answer 7

Menstrual = 4 weeks
Oestrus = 2.5 - 3 weeks

Question 8

Give an example of a seasonal long day breeder and short day breeder?

Answer 8

Long = mare
Short = ewe

Question 9

What causes seasonality in breeding?

Answer 9

The effects of melatonin on GnRH

• Patterns in light and dark cells
• long days = low melatonin
• short days = high melatonin

Question 10

What is meant by reflex ovulation?

Answer 10

The GnRH pulse generator is not sensitive enough to the high oestrogen levels to produce an LH surge. so ovulation won’t occur unless there are additional inputs from copulation
e.g. cats

Question 11

What information needs to be know for different species to manage their reproduction?

Answer 11

1. Behavioural signs of oestrus
2. How seasonality affects breeding
3. How long they are in oestrus for
4. The timing of ovulation relative to the onset of oestrus.

Question 12

Describe the reproductive patterns in a mare

Answer 12

• seasonal long day breeders
• 21 +/- 4 day cycle
• oestrus = 5 days
• ovulate 24-48 hours before the end of oestrus
• 11 month gestation

Question 13

Describe the reproductive patterns in a ewe

Answer 13

• seasonal polyoestrus
• 17 day cycle
• oestrus = 30 hours
• ovulates 20-25 hrs from the start of oestrus
• 5 month gestation

Question 14

Describe the reproductive patterns in a

Answer 14

• not seasonal
• 21 day cycle
• oestrus = 18 hours
• ovulates 20-30 hours from the start of oestrus
• 9 months gestation

Question 15

Which hormone needs to have low levels for ovulation to occur?

Answer 15

Progesterone

Question 16

What is the length of the cycle dependant on?

Answer 16

Life span of the corpus luteum - once this degenerates progesterone levels drop so GnRH is no longer inhibited so ovulation can occur

Question 17

Describe the breeding patterns in a bitch?

Answer 17

• Monoestrus = 1-3 cycles per year
• 48-72 hour ovulation
• CL lasts 60-70 days -> NO LUTEOLYTIC MECHANISm
• 4 stages : prooestrus, oestrus, metoestrus and anoestrus