Clyclicity

Question 1

2 types of repro cycles

Answer 1

Oestous

Menstural

Question 2

Oestrous

Answer 2

Predicable series of events from one ovulation to the next

Copulation occurs during this time

Question 3

Oestrus

Answer 3

Noun - the mare is in oestrus

Question 4

Oestrous

Answer 4

Length of cycle

Question 5

Typrs of eostrus

Answer 5

Polyestrus
Seasonally polyestrus (short day ewe, long day mare)

Monoestrus (dog)

Question 6

Phases of oestrous cycle

Answer 6

Follicular phase 
Luteal Phase (CL dominant structure)

Question 7

Follicular Phase

Answer 7

Follicles dominant structure

E2 secreted from follicles

From regression of CL to ovulation

Initiates sexual receptivity

20% of cycle

Question 8

Luteal Phase

Answer 8

CL dominant Structure

CL produces progesterone p4

From ovulation to regression of CL

80% of cycle

Follicles grow and regress but do not preduce high concentrations of e2

Question 9

Stages of Oestrous cycle - 4

Answer 9

Follicular phase

• Proestrus
• Oestrus

Luteal Phase

• Metoestrus
• Dioestrus

Question 10

Proestrus

Answer 10

Period immediately before estrus

Transitions from progesterone to oestrogen dominance

Progesterone declines as result of luteolysus and ends at onset of oestrus

Question 11

Oestrus

Answer 11

Part when female allows mating

Oestradiol is dominant hormone

Standing Oestrus - lordosis (back arching)

Question 12

Metoestrus

Answer 12

Oestrogen dominance to P4 dominance
(ovulation to functional CL)

Newly ovulated follicle undergoes cellular and structural remodelling to become an intr-ovarian endocrine gland = CL

Called luteinisation

Question 13

Diestrus

Answer 13

Maximum luteal function

Dominated by progesterone

Longest phase of cycle

No sexual receptivity

Ends when CL destroyed (luteolysis)

Question 14

Canine Oestrous cycle

Answer 14

Proestrus (9d), oestrus (9d), diestrus 2 months), anoestrus (5 months)

Question 15

Cats

Answer 15

Induced ovulators

proestrus, oestrus, postoestrus, dioestrus and anoestrus

Question 16

Anoestrus

Answer 16

Cyclicity is interrupted by 
Pregnancy
Nursing
Season
Nutriotion
Stress
Infection

Due to insufficient GnRH release from the hypothalamus to stimulate and maintain gonadotrophin release

Ovaries inactive- no ovulatory follicles or functional CL

Question 17

Eliminating Anoestrus

Answer 17

Improve nutrition
Remove offspring
Eliminate stress
Consider season

Question 18

Gestational Anoestrus

Answer 18

Oestrous cycles dont occur during pregnancy

P4 from CL induces negative feedback on hypo = no FSH, LH release

Question 19

Postpartum Anoestrus

Answer 19

Time after parturition where female doesnt cycle

Uterus indergoes involution to support next preg

Question 20

Silent ovulation

Answer 20

First ovulation after seasonal anoestrus is often silent in ewes

No behavioural estrus

No CL at end of anoestrus there is no progesterone

Question 21

Return to seasonal cyclicity

Answer 21

GnRH secretion must increase sufficienty to cause LH and FSH release by pituitary

Photoperiod important

Melatonin involved

Question 22

Melatonin

Answer 22

Hormone from pineal gland

Synthesised and released only at night

Stimulated GnRH in short day breeders

Inhibits GnRH on long day breeders

Question 23

Lactational Anoestrus

Answer 23

Caused by sight, smell, sound of calf

Not in bitches