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Jorge URO > Oestrus cycle and seasonality > Flashcards

Oestrus cycle and seasonality Flashcards

1
Q

Briefly describe what occurs in the oestrus cycle

A

During the oestrous cycle, waves of follicles develop until usually one becomes dominant and proceeds to ovulate (not species which have multiple offspring, like bitch / sow) and corpus luteum is formed. The CL is lysed if the female is not pregnant.

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2
Q

What are the phases of the oestrus cycle

A

pro-oestrus
oestrus
met-oestrus
dioestrus

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3
Q

What are the behaviours of a female in oestrus?

A

receptive to male (lordosis)
Mounting behaviours
Making themselves visual/aware to male they are in oestrus
Lateral deviation of tail
Urine dribbling - pheromones attract males

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4
Q

What hormonal levels are related to dioestrus?

A

high levels of progesterone

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5
Q

What horomonal levels are associated with oestrus?

A

low progesterone, high oestrogen

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6
Q

What hormones are steroids?

A

oestradiol (E2)
progesterone (P4)

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7
Q

What hormones are gonadotropins?

A

FSH
LH

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8
Q

Describe the follicular and luteal phase

A

Follicular (pro-oestrus and oestrus) - ovarian follicle development, follicles produce oestradiol -> oestrus
Luteal phase (metoestrus and dioestrus) - ovarian follicle ovulates to for a corpus luteum, produces progesterone -> diestrus

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9
Q

What signifies the end of the luteal phase?

A

luteolysis of the CL by prostaglandin F2 alpha

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10
Q

what happens to follicle development during the luteal phase?

A

Follicles are continually produced and mature - but they do not ovulate during this phase

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11
Q

What are the effects of low and high levels of oestrogen?>

A

Low levels are inhibitory to FSH and LH production from the anterior pituitary
High levels have a positive effect on GnRH production from the hypothalamus

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12
Q

What is the effect of progesterone on the hypothalamus and anterior pituitary gland?

A

inhibits GnRH, FSH and LH production

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13
Q

Describe the hormonal process of the oestrus cycle in the absence of pregnancy

A
  • elevation in oestradiol and FSH -> follicular development and oestrus behaviour
  • culminating in a surge of LH which induces ovulation (follicle -> corpus luteum)
  • corpus luteum secretes progesterone, ovary enters luteal phase, dioestrus behaviours
  • in the absence of pregnancy, the CL undergoes luteolysis due to PF2a
  • progesterone declines
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14
Q

What occurs at the end of diestrus if the female is pregnant

A

The conceptus releases a factor (maternal recognition of pregnancy signal) in mid-diestrus which prevents luteolysis
High progesterone levels maintain to keep cervix closed and allows pregnancy to develop until placenta takes over placenta production

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15
Q

What happens at ovulation

A

Follicle ovulatesd and releases an oocyte which enters the oviduct to be fertilised

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16
Q

Define polyoestrus

A

multiple cycles throughout the year

17
Q

Define seasonal polyoestrus

A

multiple cycle during one season with a transition phase between periods

18
Q

define monoestrus

A

infrequent cycles, independent of season

19
Q

Why does seasonal polyeostrus occur?

A

ensures birth at suitable time for optimum chance of offspring survival

20
Q

How is seasonal polyoestrus controlled?

A

controlled by light detected by the pineal gland which causes the release of gonadotropins which activates ovaries to stimulate follicle development

21
Q

What kind of oestrus cycle do the mare, cow, ewe, sow and queen have?

A

mare - seasonal polyoestrus (long day)
Cow - polyoestrus
Ewe - seasonal polyoestrus (short day)
Sow - polyoestrus
Queen - seasonal polyoestrus (variable)

22
Q

How long is the oestrus, dioestrus and total cycle length of the mare?

A

Oestrus - 4-8 days
Dioestrus - 15 days
Total cycle length - 21-23 days

23
Q

How long is the oestrus, dioestrus and total cycle length of the cow

A

Oestrus - 5-18 hrs
Dioestrus - 19-20 days
Total cycle length - 21-23 days

24
Q

How long is the oestrus, dioestrus and total cycle length of the ewe

A

Oestrus - 24-36hrs
Dioestrus - 19 days
Total cycle length - 21 days

25
Q

How long is the oestrus, dioestrus and total cycle length of the queen

A

Oestrus - 7-10 days
Dioestrus - 10-14 days
Total cycle length - 21 days

26
Q

How is the bitch oestrus cycle different?

A

The bitch always enters a period of anoestrus (pseudopregenancy) for 3 months whether the dog is pregnant or not
Then enter inter-oestrus (no cycling) for 7 months

27
Q

What is special about the induction of ovulation in cats?

A

ovulation is only induced by mating

28
Q

How long is oestrus in the dog?

A

9 days

Jorge URO (105 decks)

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