Bovine Reproductive Cycle Flashcards
What exogenous factors affect the bovine oestrus cycle?
Adiponectins
Stress
NEB
Photoperiod
What prevents a dominant follicle from ovulating in a follicular wave?
High progesterone
The follicle undergoes atresia
A dominant follicle will only ovulate when progesterone is low
Describe the resumption of cyclicity post-calving?
1st follicular wave ovulates and there is a short lived CL
= ovulate a silent oestrus between 14-18 days
Then normal cyclicity resumes
The cow will only start cycling again once the calf is removed
What factors reduce LH pulse frequency and delay return to cyclicity?
Sucking calf Declining NEB Poor BCS at calving Low DMI Disease
How long is the bovine oestrus cycle?
21d
Oestrus lasts how long in cow?
18h
When does the LH surge occur in relation to the onset of oestrus?
6 hours
What is the main indicator of oestrus in the cow?
Standing to be mounted
Lost some aids for detecting oestrus?
Tail paint / chalk Record keeping - observe 18 days from last oestrus Chin balls Teaser Bulls Activity meters Pedometers Heatime
What temperature should you thaw frozen semen at?
37c for 40s
What would you expect on a vaginal exam for a cow in oestrus?
Bulling string
Open cervix
How long after calving should you expect the first ovulation in a cow?
14-18d if no CL
What would you expect the uterus to feel like in a 3 month pregnant cow?
Small cotyledons
Ballot a melon sized calf
Uterine artery pulse on pregnant horn
At what stage can you palmate fremitus in the uterine artery?
5m pregnant horn
6m non-pregnant horn
From how many days can you confidently scan for pregnancy?
28
What are you looking for on a post natal check?
Endometritis
Tears
Return to cyclic activity
Whether the cervix is open or closed
When is the use of a PRID contraindicated?
Any infection of the reproductive tract
Causes vaginitis and local immunosuppression
How soon after injecting a cow that has a CL with prostaglandin would you expect to see her bulling?
2-5 days
How can you differentiate pregnancy from metritis / endometritis on ultrasound?
Foetal fluids - clear, anechoic, membranes and foetus, lining of endometritis well defined
Metritis / endometritis - slightly more hyperechoic, snow storm appearance, lining of endometrium poorly defined
What would you expect on a vaginal exam for a cow in oestrus?
Bulling string
Open cervix
How long after calving should you expect the first ovulation in a cow?
14-18d if no CL
What would you expect the uterus to feel like in a 3 month pregnant cow?
Small cotyledons
Ballot a melon sized calf
Uterine artery pulse on pregnant horn
At what stage can you palmate fremitus in the uterine artery?
5m pregnant horn
6m non-pregnant horn
From how many days can you confidently scan for pregnancy?
28
What are you looking for on a post natal check?
Endometritis
Tears
Return to cyclic activity
Whether the cervix is open or closed
When is the use of a PRID contraindicated?
Any infection of the reproductive tract
Causes vaginitis and local immunosuppression
How soon after injecting a cow that has a CL with prostaglandin would you expect to see her bulling?
2-5 days
How can you differentiate pregnancy from metritis / endometritis on ultrasound?
Foetal fluids - clear, anechoic, membranes and foetus, lining of endometritis well defined
Metritis / endometritis - slightly more hyperechoic, snow storm appearance, lining of endometrium poorly defined
What can lead to a reduced heat duration?
Lameness
Low BCS
High yield
What factors can increase the calving to conception interval and no. inseminations per pregnancy?
Drop in social status Caesarean Bad calving Lameness Mastitis Milk fever - sub clinical hypocalcaemia has a huge effect on fertility Nutrition NEB at peak lactation Hepatic lipidosis
What affect does lameness have on fertility?
Increases the calving to conception interval
Increases the no. inseminations per cow
Reduces pregnancy rate
Later resumption of cyclicity, reduced oestrus intensity and oestrus related behaviours
What is a repeat breeder?
A cow that has not conceived after 4 services
What effect can milk yield have on the expression of oestrus behaviours?
High yielded may show fewer behavioural signs of oestrus
What is the effect of the seasons on dairy cow fertility?
Poly-oestrus and non-seasonal
However…
- heat stress can reduce fertility in dairy cows in summer
- poor quality silage fed in winter may reduce fertility
