Bovine Repro1

Front 1

Describe the physiological events associated with the development of a follicular wave in cows.

Back 1

• A rise in FSH concentrations occurs at the time of follicular
emergence (“emergence”)
• As concentrations of FSH decline a single follicle will become larger
than others in the developing cohort (“selection”)
• This follicle becomes the largest (“dominant”) follicle
• A reduction in LH pulse frequency during development of dominant follicles (negative feedback of P4 and E2 on LH secretion) can lead to
atresia of the dominant follicle as it is “starved” of LH support.
Secretion of E2 and inhibin from the dominant follicle will decrease, an
increase in FSH secretion will occur & a new wave will start. This process occurs when concentrations of P4 >1 ng/mL.
• Luteolysis results in an increase in LH pulse frequency and amplitude,
an increase in concentrations of E2, positive feedback of E2 on
secretion of GnRH and release of LH, resulting in an LH & FSH surge
and ovulation. A secondary rise in FSH will occur 24 h after the LH
surge and stimulate emergence of the first follicular wave of the next
cycle

Front 2

Within what time after birth do you expect the placenta to normally be expelled?

Back 2

<12h

Front 3

Which one of the following endocrine changes occurring within the peripheral circulation of a cow best describes changes that occur around parturition?
a) An increase in concentrations of cortisol, a decline in plasma
concentrations of progesterone, an increase in plasma concentrations
of oestrogen, PGF2α and relaxin
b) An increase in plasma concentrations of cortisol progesterone and cortisol, oestrogen and a decrease in concentrations of PGF2α and relaxin
c) A decline in plasma concentrations of cortisol, progesterone,
oestrogen, PGF2α and relaxin
d) An increase in plasma concentrations of cortisol, progesterone, and
oestrogen and an increase in concentrations of PGF2α and relaxin
e) A decline in plasma concentrations of cortisol and oestrogen, an increase in plasma concentrations of progesterone, PGF2α and relaxin

Back 3

a)
• Parturition initiated by the foetus
• Increase in foetal ACTH secretion which intern stimulates foetal cortisol production
• Increase in concentrations of oestrogens prepartum
• P4 decreases in last week of gestation
• As oestrogen concentrations increase, stimulates release of
PGF2α from uterus, & myometrial oxytocin receptors
regression of CL and secretion of relaxin – softening of cervix
and relaxation of pelvic ligaments
• Increased PGF2α stimulates release of maternal oxytocin from
posterior pituitary gland which in turn stimulates further PGF2α
release by the uterus and uterine contractions

Front 4

• On average luteolysis in the bovine occurs around
which day of the oestrous cycle?
a) Day 8
b) Day 10
c) Day 13
d) Day 17
e) Day 24

Back 4

d) Day 17

Front 5

How many follicluar waves do you normally expect to see in an oestrous cycle in a cow?

Back 5

2 to 4 waves of follicular
development/cycle

Front 6

What is the average duration of oestrous cycles in
cows (days)?

Back 6

21 days (17 to 25), heifers often slightly shorter ie 20
days

Front 7

What is the average interval from onset of oestrus to
ovulation (hours)

Back 7

Ovulation 24 to 30 h after onset of oestrus

Front 8

What is the expected interval from the LH surge to
ovulation (hours)?

Back 8

24 to 28 h
Onset of oestrus coincides with surge of LH and FSH

Front 9

What is the duration of oestrus in the average cow & modern dairy cow
(hours)?

Back 9

Traditionally: 18 h (12 to 30 h).
In modern dairy cow appears to be shorter averaging around 10h
Tend to be shorter in cows under greater nutritional stress or
with higher dry matter intakes and milk yield

Front 10

How long following calving does it normally take for uterine involution to occur in the cow?

Back 10

30 days

Front 11

When do cows normally resume oestrous cycles
postpartum?

Back 11

Usually within 40 days from
calving. Can be extended in certain
circumstances

Front 12

The fertility of cows generally peaks at what interval
postpartum?

Back 12

60 to 90 days

Front 13

Draw an outline of the endocrine changes that occur:
a) during the oestrous cycle, and b) during pregnancy in the cow

Back 13