Intro to farm animal repro Flashcards
What is the most useful landmark when palpating repro tract
cervix
What does a follicle secrete
oestradiol- drives oestrus
what does a corpus luteum produce
progesterone
what is corpus luteum
highly vascularised, transient endocrine gland
what do a CL look like on Ultrasound
homogenous medium echogenicity
When does ovulation occur in the cow
12hrs after end of oestrus
If a CL is 20 mm what does this mean
CL is either growing or regressing
How long is the duration of oestrus in the cow
5-18hrs
will ovulate 12hrs after end of oestrus
How long is the oestrus cycle in the cow
21-22 days
How long is the oestrus cycle in the ewe
17 days
How long is oestrus in the ewe
24-36 hrs
ovulate 30-36 hours from begging of oestrus
How long is the oestrus cycle in the sow
21 days
how long is oestrus in the sow
48-72hrs
ovulate 35-45 hours from beggining of oestrus
What is the main oestrus detection method in the sow
back pressure test
Describe the resumption of full ovarian activity after parturition
At parturition, pituitary isrefractory to GnRH, but
FSH secretion initiated due to lack of negative feedback, this leads to emergence of an antral follicular wave
Increasing sensitivity of gonadotropes to GnRH, leading to
Increased FSH-stimulation of oestradiol production
Increased LH pulse frequency
Ovulation, often accompanied by silent oestrus
List 3 causes of physiological anoestrus
gestation
lactation/ presence of offspring
seasonality
List 2 causes of pathologuical anoestrus
stress- metabolic or heat
ovarian pathologies - Cystic ovarian disorders or Inactive ovarian activity
How does suckling cause anoestrus in the sow
Early follicular activity but
Prolactin suppresses LH secretion, thus no ovulation
Deescribe how sows return to oestrus
Weaning ‘initiates’ oestrus and LH surge within 7 days (WOI)
Weaning to oestrus interval (WOI) is affected by length of lactation / timing of weaning
what does giving synthetic GnRH do
Hastens impending cyclicity/ return to oestrus
Hastens ovulation by inducing LH surge. - if dominant follicle there
“Force” ovulation/luteinisation of cystic structures
what does giving synthetic FSH do
Stimulates antral follicular growth- results in multiple dominant follicles- embryo transfer
How is synthetic progesterones used
Progesterone has a negative feedback effect upon the hypothalamus and anterior pituitary
Suppress the hypothalamic-gonadal axis thus:
Used as method of inducing/synchronising oestrus following withdrawal of the product
what does prostaglandin F2a do
Lysis of the mature CL, causing progesterone to decline
Smooth muscle contraction i.e. ecbolic effect on uterus
After administration of PGF2a when will the cow come into oestrus
3-4 days after PGF2a administration- if there is a mature follicle
Why can’t we use 2 doses of PGF2a in sows
Cl only responsive day 11-16
List 3 ways to stimulate onset of early cyclicity in sheep
Melatonin
Progestogen sponges in combination with eCG/GnRH
Ram effect
