Female Reproductive Physiology IV: Modulating Cyclicity

Mares have a short _____, uterine recovery?

Puerperium

Horses gestation can last usually how long?

330-345 days

What is foal heat?

First heat period following foaling usually 7 days after birth

What is polyesterous?

Year round breeding (cows and sows)

What is seasonally polyesterous?

Several esters cycles followed by anesterous (horses sheep goat cats)

What is a monstrous animal?

One estrous cycle followed by prolonged anestrous (dogs)

Anestrous is characterized by what?

Low estrogen and reproductive activity

What kind of animals are long day breeders?

Mares and queens

What animals are short day breeders?

Sheep and goats

What is the primary controller of the reproductive cycles?

Light

What is going to respond to light in the brain? What will it produce?

Pineal gland releasing melatonin in response to low light

Explain how light gets to the pineal gland?

The retina will transfer light to the retinal hypothalamic tract (RHT) and travel to hypothalamic suprachiasmatic nucleus (SCN) which will inhibit the pineal gland if there is too much light

If we have high light low melatonin release what type of breeding habits does this support?

Long day breeders

Explain how low melatonin secretion leads to cyclicality in long day breeders?

RFRP neurons will be stimulated releasing RFRP-3 stimulating kiss1 neurons to increase GnRH and gonadotrophin to result in cyclicality

Seasonality can also affect when an animal does what?

Goes into puberty

Explain how social conditions affect puberty?

Large groups or introduction of males can speed up puberty

Lactation causes ____ of ovulation in sows, _____ in cats and cows?

Complete inhibition;

Partial suppression

Explain how suckling can inhibit cyclicity?

Suckling will inhibit dopamine with results in prolactin

Prolactin will typically inhibit GnRH meaning no cycles

What three hormones contribute to the suppression of GnRH during lactation?

Dopamine suppression

Oxytocin production

Prolactin production

During weening what hormone do we see a surge of?

LH resulting in return of cyclicity

An animal w/ a low body weight can ____ ovulation?

Delay

Why does nutrition matter for ovulation?

IGF-1 and thyroid hormone from nutrition control steroidogenesis

BG levels are detected by hypothalamus

How does leptin factor into cyclicity?

Leptin targets Kispeptin neurons and can stimulate GnRH from the preoptic nucleus

A leptin deficiency may ____ estrus?

Delay

How does negative energy balance in early lactation delay cyclicity in cows?

Milk production takes more energy than the cow is taking in and therefore the body will not cycle b/c nutrients is low

What is flushing?

Giving high quality feeds prior to the start of breeding to increase repro performance

How does old age change cyclicity?

Reduction of estrogen will reduce gonadotrophs (specifically LH) resulting in no ovulation. Lack of follicles will increase FSH and less estrogen will neg feedback. There will be a short estrus cycle