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REPRO > The oestrus cycle and seasonality > Flashcards

The oestrus cycle and seasonality Flashcards

1
Q

Define polyoestrus

A

multiple cycles throughout the year

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2
Q

Define Seasonal polyoestrus

A

multiple cycles during one season, for the rest of the year they are anoestrus

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3
Q

What are the two types of season?

A 
Long day (spring, mare)
Short day (autumn, ewe)
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4
Q

Define monoestrus

A

infrequent cycles, independent of season

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5
Q

What is the purpose of seasonality?

A

This ensures birth occurs at a suitable time with regards to weather and nutrition – optimum chance of offspring survival

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6
Q

How is seasonality controlled?

A

Seasonality is controlled by light, Detected by pineal gland.
This activates brain centres leading to release of gonadotrophins (FSH & LH) which activate ovary stimulating development of follicles, secretion of oestrogen and progesterone which in turn influence behaviour (receptivity) and uterine environment.

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7
Q

What is the difference between an oestrus and dioestrus female?

A

The oestrus female is receptive to the male (lordosis) & has high levels of oestrogens whereas the dioestrous female rejects the male & has high levels of progesterone.

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8
Q

Name the possible stages of the oestrus cycle

A

Pro-oestrus – phase immediately before oestrus
Oestrus
Met-oestrus– succeeds oestrus, corpus luteum forms
Dioestrus

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9
Q

Which stages of the oestrus cycle equate to the follicular stage of the ovary?

A

Pro-oestrus and oestrus
Ovarian follicles mature and secrete increasing concentrations of oestradiol into blood
This leads to oestrous behaviour

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10
Q

Which stages of the oestrus cycle equate to the luteal phase of the ovary?

A

Metoestrus & dioestrus
Ovarian follicles ovulate to produce >1 corpora lutea (CL) and this CL secretes progesterone into blood
This stage ends with luteolysis of the CL by prostaglandin F2a the follicles continue to develop but fail to ovulate

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11
Q

What are the effects of oestrogens produced in (pro)oestrus/the follicular phase?

A

result in behaviour to allow mating
prepare external genitalia & vagina for mating: increased blood flow
increase mucus production in cervical glands (useful to detect oestrus in some species): dogs & cows bleed
stimulate follicular growth & maturation in ovaries
prepare uterine environment for sperm transport & implantation of fertilised oocytes ie hypertrophy of endometrial epithelium & glandular enlargement

contribute to growth & development of mammary tissue
prepare uterus for parturition (birth)

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12
Q

What are the effects of progesterone from the luteal phase/dioestrus/metoestrus?

A

increased secretion by glands of uterine epithelium & more complex gland morphology
gland secretions contain nutrients for fertilised oocytes (uterine milk)
prepares uterus for zygote
behaviour (rejects male)

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13
Q

What are the general effects of the gonadotrophins LH and FSH?

A

FSH- stimulates the maturation of germ cells/follicles

LH stimulates the production of steroids oestrogen and progesterone

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14
Q

In the follicular stage, a slow increase in FSH and oestrogen causes….

A

Follicular development and eventually a surge in LH which initiates ovulation

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15
Q

Is the mare mono or polyoestrus?

A

Seasonal polyoestrus- although some cycle continually

Their season is Long day (april- august)

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16
Q

How long is the oestrus cycle in the mare?

When do they ovulate?

A

Oestrus: 6 days
Dioestrus: 15 days
Total cycle length: 21-23 days
Ovulation: last day of oestrus / before end of oestrus

17
Q

In mares how can we detect the presence of a CL?

A

There is a sharp rise in progesterone

18
Q

Are cows polyoestrus or monoestrus?

A

Polyoestrus as we have bred out seasonality

19
Q

How long is the oestrus cycle in the cow?

When do they ovulate?

A

Oestrus: 8 hours
Dioestrus: 19-20 days
Total cycle length: 18-24 days
Ovulation: 12 hours after the end of oestrus (24-32h after onset)

20
Q

Are ewes polyoestrus or monoestrus?

A

Seasonal polyoestrus

Short day breeder (October – February)

21
Q

How long is the oestrus cycle in the ewe?

When do they ovulate?

A

Oestrus: 30 hours
Dioestrus: 15-16 days
Total cycle length: 17 days
Ovulation towards the end of oestrus

22
Q

Are sows polyoestrus or monoestrus?

A

Polyoestrus (wild pigs may be seasonal)

23
Q

How long is the oestrus cycle in the sow?

When do they ovulate?

A

Oestrus: 53 hours
Dioestrus: 19 days
Total cycle length: 21 days
Ovulation: 35-45 hours after the start of oestrus

24
Q

Are goats polyoestrus or monoestrus?

A

Seasonal polyoestrus

Short day breeder (August to February

25
Q

How long is the oestrus cycle in the goat?

When do they ovulate?

A

Oestrus: 30-40 hours
Dioestrus: 20-21 days
Total cycle length: 21-22 days
Ovulation: 12-36 hours after the start of oestrus

26
Q

Are bitches polyoestrus or monoestrus?

A

Monoestrus

27
Q

How long is the oestrus cycle in the bitch?

When do they ovulate?

A 
Pro-oestrus: 9 days
Oestrus: 9 days
Ovulation: 1-2 days after onset of oestrus
Met-oestrus
	70-80d if measured by regression of CL 
	130-140d if measured by endometrium repair
Anoestrus: 3 months
Interoestrus: 7 months
28
Q

Are queens polyoestrus or monoestrus?

A

Seasonal polyoestrus
Cycling in 10h daylight March to September but influenced by environmental factors, presence of other cats and artificial light

29
Q

How long is the oestrus cycle in the queen?

When do they ovulate?

A

Oestrus: 7-10 days
Dioestrus:10-14 days
Total cycle length: 21 days
Ovulation dependent on mating (induced ovulator)

30
Q

Are ferrets (jills) polyoestrus or monoestrus?

A

Seasonal polyoestrus

31
Q

How long is the oestrus cycle in the ferret?

When do they ovulate?

A

Oestrus if mated ~14 days if unmated <6 months

Ovulation dependent on mating (induced ovulator) 30-40h after mating

32
Q

What senses day length?

A

Light sensed by the retina and processed by the hypothalamus

33
Q

Where is melatonin produced?

A

The pineal gland

34
Q

Decreasing day length (increasing dark) leads to an …………………. in melatonin

A

Increase

35
Q

Short day breeders are stimulated by ………………. melatonin

A

increasing

REPRO (30 decks)

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