Lecture 6

What is a characteristic feature of monotocous species in terms of offspring?

They produce one offspring.

What does the dominant follicle secrete to decrease FSH secretion in monotocous species?

Inhibin.

What distinguishes polytocous species in terms of offspring?

They produce many offspring.

What is the main driver of seasonal breeders' reproductive cycles?

Photoperiod.

Which animal is classified as a long day breeder?

Mares.

Which species are short day breeders

Small ruminants

How does photoperiod affect a seasonal breeder’s oestrus cycle. Provide an example of the regulation pathway

Long day breeders → Lots of light → sensory neurons in retina stimulate excitatory neurons → stimulate inhibitory neurons in pineal gland → low melatonin release → stimulation of RFRP neurons → increases in RFRP-3 → stimulation of long day kiss neurons → release of high kiss peptin 10 release → high GnRH → high FSH + LH

How long is the oestrus cycle for goats?

21 days.

How long is the oestrus duration in goats

24-26 hours

How long is the sheep oestrus cycle

18 days

How long is the duration of oestrus in sheep?

32-40 hours.

How long is the oestrus cycle in cows

21 days

What is the duration of oestrus in cows?

18 hours.

What is the oestrus duration in pigs?

2-3 days.

How long is the oestrus cycle in pigs

21 days.

How long is the oestrus cycle of horses

Approximately 21 days.

How long is oestrus duration in horses

4-8 days

What marks the first day of oestrus in dogs and why and how long does it last for

LH surge because oestrogen levels don’t peak in oestrus but rather in prooestrus. lasts for 24-48 hours

When does ovulation occur in dogs

approximately 2 to 3 days after the LH peak

How long is oestrus cycle in dogs

8 days approx

What is unique about the oestrus cycle of dogs

Oocytes are ovulated as primary oocytes and need to undergo a maturation phase which takes 48-72 hours before they can be fertilised. 

They also don’t have a distinct luteolysis

When do pigs typically ovulate

30-45 hours after start of heat

When do cows typically ovulate

10-11 hours after oestrus ends

When do sheep typically ovulate

Around time heat ends

What percentage of spontaneous ovulation can cats have?

Up to 30%.

What is the difference between induced and spontaneous ovulators

Induced ovulators release eggs only after mating, while spontaneous ovulators do so cyclically regardless of mating.

When do goats typically ovulate

Around time their heat ends

What is required for ovulation to occur in induced ovulators like cats?

Mating.

How does the female cycle work in felines

Mating results in a decreases of oestradiol production and an increases in prostglandinlevels, leading to ovulation.

When there is no mating, they have only prooestrus, postoestrus and oestrus phases

If they ovulate but no pregnancy results, they are pseudopregnant for 40 days

What marks the beginning of the menstrual cycle in humans?

Menses, characterized by bleeding.

What is a camel’s LH surge dependent on in order to promote ovulation

LH inducing factor in semen

How long is a menstrual cycle

28 days

What are the 2 different phases of the menstrual cycle

the proliferative and secretory phase

What occurs in the secretory vs proliferative phases

The proliferative phase follows luteolysis and is where oestrogen begins to rise and the endometrium starts to thicken after it has just been shed following luteolysis

The secretory phase is where the uterine glands are secreting urin milk and prostaglandin starts to increase