Oestrous Cycles In Large Animals

Question 1

Specific features of the bovine oestrous cycle
-duration

Answer 1

Avg 21 days (range 18-24), 17 days luteal phase,4 days follicular phase

Question 2

What is appearance of cows vulva:
-before oestrus
-during and after oestrus
-metoestrus- after oestrus

Answer 2

1. Secretions can be seen coming out & swollen
2. Clear viscus mucus and dried mucus on tail
3. Accumulate mucus and RBC’s mixup to form a red stringy type mucus

Question 3

What changes in steroid and Gonadotrophin hormones can be seen in bovine oestrous cycle

Answer 3

-Progesterone rises slowly, reaches a plateau, declines abruptly at luteolysis
LH pulsatility changes depending on progesterone concentrations (negative feedback on GnRH pulses)
-Oestradiol rises rapidly in the follicular phase inducing the GnRH and gonadotrophin surge
-Small oestradiol rise seen with DF development during the luteal phase (see next slide)
-FSH rises when DF ovulates or becomes atretic, 2-3 times during the cycle

Question 4

Describe the hormonal changes that occur in oestrus Cycle in bovine

Answer 4

On anki bruh

Question 5

-Each follicle wave emerges following an…
-DF selection occurs during…
-The functional DF secretes… and suppresses…

Answer 5

-FSH rise
-FSH decline
-Oestradiol and inhibin & suppresses FSH

Question 6

Lack of LH pulses means…

Answer 6

DF has become atretic

Question 7

What is luteolysis

Answer 7

structural and functional degradation of the corpus luteum, which occurs at the end of the luteal phase of both the estrous and menstrual cycles. Preceded by loss of the capacity to synthesize and secrete progesterone.

Question 8

Whats the difference between 2-wave and 3-wave cycles in cows?

Answer 8

The number of dominant follicles selected during cycle

Question 9

Which species usually selects single dominant follicle

Answer 9

Mare

Question 10

What kind of breeder is the mare?

Answer 10

Seasonal, long day breeder- breeding season in spring and summer

Question 11

What is the follicular phase called as in the mare?

Answer 11

Oestrus phase

Question 12

In the mare, ovulation occurs…

Answer 12

Before the end of oestrous (follicular phase) period
1-2 days before

Question 13

What is luteinisation?

Answer 13

process by which elements of the ovarian follicle, usually including both theca interna and granulosa cells, are provoked by the ovulatory stimulus to develop into the corpus luteum/luteal cells

Question 14

Describe the oestrus cycle of the mare
-how long is cycle

Answer 14

-Oestrus phase; increased Oestradiol for around 5 days, supported by rise in LH (supports growth) (no distinct surge as in other species)
-rapid luteinisation & increased progesterone due to peak LH levels which leads to selection of DF during prog decline
-abrupt decline at luteolysis around day 14
-oestrous phase again with ^ Oestradiol for 5 more days or so.

-cycle on avg 21 days with luteal phase 14 days and long oestrous 5-7 days

Question 15

Why are mares teased during reeding season (tail raised to the side)

Answer 15

To allow farmer to see when its coming into oestrus cycle time (vulva looks like its popping out slightly)