Reproduction: Oestrus Cycle and Repro Physiology Flashcards
What effects the release of neurotransmitters for release of GnRH from the hypothalamus?
- Energy
- Stress
- Photoperiod
How does negative energy balance effect cows return to cyclicity?
Increases
What are the different signs of oestrus?
What is the definited sign of oestrus?
- Mucus discharge, swelling of vulva
- Holding milk, bawling, restless
- Mounting other cows
- Licking
- Chin resting
- Standing to be mounted- in oestrus
What is the most common duration of standing heat?
3 hours
What can be used as mount detectors?
- Paint/chalk or kamar/ambic
- Cow is detected when standing
How do pedometers detect heat?
Activity increases
What should be considered about AI routine if reduced pregnancy rates?
- Has flask become empty and sperm thawed then refrozen
- Have used fingers rather than tweezers
- Thaw at 37 for 30 seconds
- Dry thoroughly
- Load gun, snip end off straw
- Disposable sheath
- Keep warm
- That one at time
Why was AI introduced?
- Genetic pool
- No bull care
- reduce sexually transmitted disease
What is the AM: PM rule
If seen on heat at AM serve PM
If seen on heat PM serve AM
What causes return to cyclicity if cow is not pregnant?
- Progesterone by CL
- Oxtyocin- anterior pituitary
- Maternal recognition does not occur
- Endometrium develops oxytocin receptors
- If no implantation causes release of PGF2
Interferon TAU is released in pregnancy
How does calf trigger calving?
- Signal?
- Calf produces ACTH from anterior pitutary
- Causes fetal adrenal gland produce cortisol
- Cortisol causes calf lung to develop
- Causes prostoglandin release and reduction in progesterone
To what hormone do selected follicles develop receptors to and become dominant?
LH
What is the dominant hormone in dioestrus?
Progesterone
How is metoestrus diagnosed?
2 small ovaries and blood tinged vaginal discharge
What hormone does the developing follicle produce?
Oestradiol
What is the function of oestradiol?
Stimulate oestrus behaviour
What inhibits LH pulse development?
- NEB
- Poor DMI
- Diseases- mastitis, lameness
How does increasing the size of the group of breeding females affect oestrus and number of cow mounts?
Increases duration of oestrus/no of cow mounts
Describe the changes in hormones from Oestrus to Proestrus
Oestrus:
* Oestrogen very high
* Causes LH surge
* FSH increases not as much
Metoestrus
* FSH increases and falls stimulate follicles
* Follicle remodels to CL- starts producing progesterone
* LH pulses
Dioestrus
* Progesterone very high
* FSH continues to cause follicle recruitment and maturation
* Progesterone from CL prevents ovulation- no high oestrogen
* Progesterone falls as CL luteolysis occurs from prostofglandin- no zygote
Proestrus
* Progesterone still falling
* Oestrogen starting to increase
* LH starting to increase
