REPRO 2 Oestrus vs menstrual Flashcards
What is the luteal phase?
- latter phase of the menstrual cycle or the earlier phase of the estrous cycle. It begins with the formation of the corpus luteum and ends in either pregnancy or luteolysis
Oestrus Vs Menstral cycles
Menstrual
1. Primates
2. extensively renewed at the start of the follicular phase. Seen as
menstrual bleeding.
3. 4 week cycle
4. Day 0/1 – low oestrogen (menses)
Oestrus
1. Non primates
2. No menstrual bleeding but some blood spotting seen at the peak oestrogen levels
in some species (e.g. bitch in oestrus)
3. SHORTER FOLLICULAR PHASE 2.5 – 3 week
cycle (follicles develop throughout luteal
phase)
4. Day 0/1 – high oestrogen animal sexually
receptive
What is the animals point of reference as primates are the only animals that menstruate?
- follicles produce oestrogen
- progesterone from corpus luteum after ovulation
- ————– - day one of oestrus
- Oestrus = behaviour showing that they’re sexually receptive = in heat
What are things we need to consider with our domestic species oestrus cycles
- Seasonal or non seasonal?
- Mono or polyoestrus? having only 1 or more than one period of estrus in a year
- Reflex or spontaneous ovulators?
What type of breeders are cows + list other animals that come under this category. What does it mean?
- do the same for mares
- sheep
- dog
- Polyestrus non seasonal = Cow, queen, pig, rodent = come into oestrus many times a year
- Seasonal polyestrus = Mares = only in spring cycle (long day)
- SP = Sheep, doe, elk, nannny = autumn breeders (short day)
- Seasonal Monoestrus = dog, wolf, fox, bear
When cycling, what is occurring hormonally?
- Peak of oestrogen ultimately driven by inc in GnRH = FSH = LH = cells produce oestrogen
When see Oestrogen what should you immediately think?!
THINK GnRH think BRAIN!
why does difference in seasons affect breeding?
- sensory ganglion cells pick up the pattern of light and dark
- impulses sent to pineal gland which responds to changes in light and dark, producing MELATONIN
- Melatonin release into blood stream and dramatically affects GnRH production
How does length of day affect melatonin?
- long days = low melatonin
- long nights = lots of melatonin
Way this affects animals is SPECIES specific
Horse VS Sheep reacting to melatonin
- Horse- low melatonin in spring = inc GnRH
2. Sheep = reduced GnRH
How is seasonality in breeding controlled?
- by the effect of melatonin on GnRH release
What are the 2 types of ovulators and what does each mean?
- Reflex and Spontaneous
- S = Ovulate anyway
- R = some reserve ovulation for when mated.
Reflex ovulators
- GnRH pulse generator not sensitive enough to high oestrogen to induce an LH surge.
- Therefore only have follicular phase
- Need additional inputs to brain to induce ovulation = stretch inputs form vagina and sensory inputs all combine to inc GnRH
- e.g. CAT, Camel, Rabbit, ferret
Talk about neuro travel for reflex ovulators
- Sensory receptors in vagina
- Peripheral therefore to spinal chord, then brain
- synapse in area of hypothalamus called surge centre
- more GnRH therefore more LH to produce ovulation
Why is it important for ferrets to either mate or be spayed, not be with neither?
- no mate
- no ovulation, for some reason produce loads of oestrogen which inc
- oestrogen suppresses bone marrow
Mare oestrus cycle:
- polyoestrus and spontaneous ovulators
- Spring breeding season
- 11 month pregnancy
- seasonal LONG day breeders
- 21 + - 4 day cycle
- Oestrus (long) 5 days +- 2
- Ovulate 24-48 hours before end oestrus (attract males)
Oestrus cycle of sheep
- seasonal polyoestrus and spontaneous ovulators
- 5 month gestation
- 17 day cycle
- Oestrus lasts 30 hrs
- Ovulates 20-25 hrs from start oestrus
- short day breeders
Oestrus cycle of cow
- polyoestrus and spontaneous ovulators
- Not seasonal
- 21 day cycle
- Oestrus lasts 18 hrs (short)
- Ovulates 20-30 hrs from start oestrus
How does the folicle grow throughout the oestrus cycle?
- small primordial follicle
- primary, secondary, teritary follicle
3.
During cow cycle, around day 8/9, dominant follicle, producing lots of oestrogen but DOESN’T ovulate. Why?
- No ovulation in dairy cows at day 8/9
- as no LH surge due to Progesterone
- P ALWAYS inhibits brain and pituitary therefore inhibits LH release
- no ovulation if progesterone EVER no matter the stage
If progesterone falls what happens?
- Less suppression of HPA axis
- LH then produced in large amounts
- supports developing follicle
- Ovulation
How can you divide the oestrus cycle up? e.g. cow
Cow = 21 days
- Metestrus (0-5)
- Diestrus (5-17) = lots of progesterone
- Proestrus (17-20
- Oestrus (20-21) = behavioural oestrus
Describe the first follicular wave in a cow
Follicles are recruited then selected, then some become dominant
Day 0 - 9
1. FSH released, binds to follicles and those develop
2. loads develop initially (5-10)
3. BEcome selected
4. Most selected die off. 1 (cow) becomes dominant = big follicle = produce loads of oestrogen = inhibits FSH
5. Little follicles need FSH to develop so therefore only 1 dominant
Describe the second follicular wave in a cow
Day 10 to 21
Luteolysis = around day 17
1. exactly same
2. differencce = luteolysis = corpus leuteum dies = stops producing progesterone = stops inhibiting HPA axis = lots mroe LH = folicle produces MORE oestrogen = positive feedback
Why do the follicles doe off in wave 1?
progesterone too high, LH pulse too low so these all die off so second wave starts
Follicles are X dependent in first wave and why
X = FSH dependent
Because this starts the recruitment/ development
When follicles are selected they’re X dependent and why?
X = LH dependent
LH important for further development adn producign ltos of precursors for oestrogen
What determines which follicle becomes dominant?
- most LH receptors on it
Why is luteolysis so important?
Progesterone stopped so ovulation occurs. If not then never ovulate
If progesterone is high/ low what are LH pulse frequency like?
What does this tell us
is P is high then LH pulses are VERY low
If P is low then LH pulse frequency is HIGH until ovulation
1. Tells us that progesterone has a profound effect on GnRH and therefore LH
Bitch Ovarian cycle
- Proestrus = incredbly high oestrogen levels (many males come) (bleeding) = vulva swollen, bloody discharge, attracted to male but F doesn’t mate, 9ish days (variable)
- Oestrus = roughly 9 days. Accepts male
- Metoestrus/ dioestrus = progesterone dominant as ovulate from corpus luteum. for 60-70 dasy
- Anoestrus = ovarian inactivity between end of dioestrus and start of next pro oestrus
In bitch How does level of FSH change?
- high in anestrus (5 months) as no ovarian hormones to inhibit
- Low in proestrus (9 days) as oestrus produced that inhibits
- Surge in proestrus/estrus line
- then fall
Describe bitch’s oestrus cycle
- spontaneous ovulators
- monoestrus
- most ovulation occurs 48-72 hours after LH surge
- Corpus luteum lasts 60-70 days = NO LUTEOLYTIC mechanism
- Day 0 = peak in LH convention, late pro oestrus/ early oestrus
Unique thing about bitch
Ovulation takes 2-3 days and progesterone starts to increase BEFORE ovulation
