Bovine Therio - 1 Estrous Cycle and Reproductive Endocrinology Flashcards
Bovine are what kind of breeders
Non seasonal polycyclic
Bovine female reaches puberty at what age
7-18mths (avg. 10mths)
The bovine oestrous cycle length is
18-24days (avg. 21days)
The bovine oestrus cycle is divided into two phases, name and define them
Luteal phase: 14-18days the period following ovulation when the corpus luteum is formed (met-estrus and diestrus)
Follicular phase: 4-6days the period following the demise of the CL until ovulation (pro-estrus and oestrus)
Bovine oestrous cycle is divided into how much follicular waves and how long does each wave take
2-3 follicular waves
7-10days appart
During bovine oestrous cycle, what happens to the ovulatory follicle during the follicular phase
Maturation and ovulation, the oocyte is released into the oviduct allowing the potential for fertilization
The bovine oestrous cycle is regulated by hormones from various locations, name them and their location
Gonadotrophin-releasing hormone (GnRH) - Hypothalamus
Follicle-stimulating hormone (FSH) & Luteinizing hormones (LH) - Anterior pituitary
Progesterone (P4), Estradiol (E2) & Inhibin - Ovaries
Prostaglandin F2α (PGF) -Uterus
Describe Bovine Luteal phase Metoestrus
- Day
- CL?
- Uterine tone
- Other?
Day 1-4
Ovulation depression > Corpus haemorrhagicum > Early CL
Within 48hrs - CL 1.4cm
Uterus - slight tone/oedema/flaccid
Metoestral bleeding (only occurs in cattle
Ova Transport time 3-4 days
Describe Bovine Luteal phase Diestrus
- Day
- Dominant hormone
- CL
- Uterine tone
- Cervix
Day 6-18 Progesterone Palpable papilla (CL) Flaccid uterus Cervix closed
In non pregnancy, describe the continuation of follicular development (pro-oestrus)
PGF secreted by the endometrium > regression of the CL > fall in progesterone > BPO axis > GnRH > FSH > Follicular development
Describe Bovine Follicular phase Pro-oestrus
- Day
- Dominant hormone
- CL
- Follicle
- Uterine tone
- Vulva
- Signs
Day 19-20 FSH CL 1.5-2cm F 1.5-2cm Moderate uterine tone Vulva swollen Signs: slight mucous, mounting behaviour
Describe Bovine Follicular phase Oestrus (prior to ovulation)
- Day
- Dominant hormone
- CL
- Follicle
- Uterine tone
- Cervix
- Vagina
- Vulva
- Signs
Day 21 Oestrogens (esp. Estradial) & baseline progesterone (due to regression of CL) CL 1.5cm Rapidly growing dominant F Marked uterine tone Dilated cervix Vagina mm pink Vulval oedema Signs: thick mucous discharge, oestrus behaviour
What is the duration of bovine oestrus (not oestrous cycle)
8-12hrs
When does ovulation occur in the bovine
After END of oestrus
When is the best time (best fertility) to AI a bovine
Mid-oestrus to few hrs after end of oestrus
Ovulation in the bovine, is the beginning of the oestrus cycle (day 0). Define it.
The rupturing of the follicle that releases the ovum
The same hormones that control the timing of ovulation in the bovine, control what else
Behavioural estrus (heat)
Both timing of ovulation and estrus is controlled by the same hormones in the bovine. What hormone is this? Where does it act and why is this important
Estradiol on the hypothalamus, uterus and higher brain (behavioural change). Easier to detect optimum fertility
After ovulation in the bovine, the ruptured follicle becomes what?
Corpus luteum
The bovine CL is formed under the influence of what
Pituitary LH
The bovine CL decides the length of the oestrus cycle?
Yes
What is the function of the bovine CL
Secretion of progesterone
The bovine CL is responsive to PGF after how many days
5/6
receptors acquired
What day does the bovine CL reach max size
7-8th CL 2-2.5cm
