THERIO- Ovarian Cyclicity

cow

• Estrogen- sudden rise just before the onset of behavioral estrus, stimulate LH surge decline to basal level at the time of ovulation.

• Progesterone- decrease to basal level – end of diestrus.

o Removes the block to the anterior pituitary which allows sudden release of FSH.

Mare

• FSH peaks- occurs mid-diestrus, not associated with any comparable rise in LH.

• LH- gradual increase and persistence of elevated levels for 5-6 days.

• Estrogen- peaks during estrus.

ewe

• Estrogen- rise before the onset of estrus, peaks about 14 hours before ovulation.

• LH- surge after estrogen peak.

• Progesterone- peaks 5.5 – 9.5 day of diestrus, decline on 12 da of diestrus.

• FSH surge- decline of progesterone, cause growth of new follicle and initiative of new estrus cycle.

sow

• FSH surge- start of regression of corpus luteum.

• Estrogen- rise starts at the beginning of regression of corpus luteum, peaks at 48 hours before onset of estrus.

• LH surge- beginning of estrus, 8-15hours after estrogen peak.

• Progesterone- decline on the12th day of estrus.

bitch

• Estrogen- rapid rise just before the onset of standing heat.

• LH- surge following estrogen rise.

• Progesterone- start to rise before ovulation occurs.

o Pre-ovulatory rise in progesterone- provides stimulus for bitch to accept male persistence for a long period (prolonged luteal phase).

queen

• LH surge- minutes after intromission with a duration of 4-14 hours.