The oestrus cycle Flashcards
Give examples of polyoestrus animals that cycle constantly throughout the year?
Cow, pig and rodent
Give examples of seasonal oestrus cycle animals that cycle during a specific season?
Long day (spring, mare and deer) Short day (autumn, ewe)
Give and example of a monoestrus animal that has infrequent cycles independent of season?
Dogs.
What are some of the methods used to manipulate seasonal breeders?
Artificial change to photoperiod i.e. put mares
& stallions under lights at Xmas.
Physical change to photoperiod i.e. “shuttle”
stallions travel from northern to southern hemispheres
biannually.
What are the signs of oestrus in the female?
— Is receptive to the male (lordosis) &
— has high levels of oestrogens
What are the signs of dioestrus in the female?
— rejects the male &
— has high levels of progesterone
What are phases of the oestrus cycle?
Prooestrus* — phase immediately before oestrus Oestrus Metoestrus* — succeeds oestrus, corpus luteum forms Dioestrus *not obvious in all species
What stage of the oestrus cycle is the bitch likely to be in during the follicular and luteolytic phase and which hormone governs this?
Pro-oestrus and oestrus.
Oestrogen.
What stage of the oestrus cycle is the bitch likely to be in during the luteal phase and which hormone governs this?
Metoestrus and dioestrus
Progesterone
What does FSH do?
Stimulates maturation of germ cells (all stages of gametes)
What does LH do in the male and the female?
. luteinising hormone stimulates production & secretion of steroids:
— testosterone in testes
- oestrogen & progesterone in ovaries
What are some oestrus detection methods used in cattle?
Kamars, pedometers, estrotect, GPS, Van Eerdenbergs scoring, Low plasma/milk progesterone, crystallisation patterns in the vaginal mucus, a fall in body temperature prior to oestrus, a reduction in vaginal pH
10 15 Days in relation to ovulation
What factors can inhibit oestrus behaviour in cows?
— Hard, non-supportive floor is best — Concrete reduces oestrous behaviour by up to 50% especially when wet and slippery — High environmental temperature — Overcrowding — Recent mixing / stress — Lameness - FEEDING Think of poor observation first
What can be used in cows to synchronise ovulation?
Ovsynch
Signs of oestrus in the sow?
VuIva swollen and congested prior to oestrus Seeks the boar Stands firmly to be mounted (the back pressure test (she won’t move when you put pressure on her; very reliable)
Signs of oestrus in the mare?
Detection of a large follicle (>20mm) in absence of a CL)
(by palpation or ultrasound examination)
Demonstration of follicle size, follicle wall thickening, follicle softening on ultrasound examination
How long does proestrus typically last in the bitch and what are the signs?
— Very long (classically 9 days) — Bitch is attractive to the male but will not allow mating —Vulvalswelling — Presence of a serosanguinous discharge (bloody discharge from vulva)
What are the signs of oestrus in the bitch and what is the average length?
. Oestrus: 9 days — Standing to be mated — Deviation of tail — Discharge becomes paler in colour — Reduction in vulvaloedema
What is the most effective method of oestrus detection in the bitch?
Vaginal cytology
Should see anucleate epithelial cells during oestrus
What kind of ovulators are cats?
Induced ovulators.
LH response to mating decreases with each day
of oestrus and follicles ultimately regress
What are signs of oestrus in the queen?
. Increased vocalisation, rubbing and rolling
. Increased activity and will seek tom
. Possible slight mucoid vulval discharge
What is an induced ovulator? And what species exhibit this?
— The presence of an antral follicle and increased oestrogen are still prerequisite for LH release and ovulation HOWEVER, copulation results in neuro-endocrine response resulting in LH release and then ovulation
- Examples: cat, rabbit, ferret, mink, camelids
What are the series of hormonal events that lead to dominant follicle selection?
Oestradiol and inhibin increase causing FSH to drop and subordinate follicles to degenerate.
What sequence of hormonal events initiates ovulation?
Non pregnant uterus secretes PGF2a, causing luteolysis, meaning progesterone drops, oestradiol is secreted from ovulatory follicle causing an LH surge and next ovulation.
