Detection and synchronisation of oestrus and AI Flashcards
What is the estimated cost of a missed heat in a dairy herd?
$100
-Pregnant later, shorter lactation, increased likelihood of induction
In a paddock how can you tell which cows are in heat?
They are the ones standing still and being mounted
What are some secondary oestrous behaviour signs?
Attempt to mount other cows Disorientated mounting Vulval mucus discharge Vulval swelling Restlessness - Heads up SAG's - sexually active groups Sniffing Licking Rubbing Aggressive behaviour Chin resting Increased amublatory activity Poor milk let down Rubbed pin bones and base of tail
During oestrous what will the concentrations of progesterone, oestradiol, LH and FSH be?
Progesterone - Low
Oestradiol - High
LH - Increase in pulse frequency and a cumulative surge
FSH - Increases because of LH
How do the number of cows simultaneously being in oestrus affect behaviour?
Get more signs of oestrus
What are some factors that affect oestrous behaviour?
Environment Stress Lameness Moving animals (increases) Climate Health Nutrition and milk yield Age Breed (Less if Bos indicus) Synchronisation method
Why if you use GnRH to induce ovulation, that many cows won’t show oestrous behaviour?
May not reach the threshold estrogen level to show heat
What are some ways to improve the efficiency and PPV of heat detection?
Improve cow identification and record keeping
Spend time observing cow behaviour - at least twice/day
Place suspicious cows in with a group of oestrous cows
Use heat detection aids
Optimise nutrition and health
Train staff
Sync oestrous if significant problem
What are some heat detection aids?
Tail pain Marking crayons Kamars / Bulling beacons Estrus alert - 'scratchie' Pedometer
How can you use submission rates to evaluate the sensitivity of oestrous detection?
Within a 3 week period over 85% should be submitted for AI
-Since all cows should come into oestrus in a 3 week period
What 2 things can low submission rates indicate?
Either poor oestrous detection
Or a high proportion of non-cycling cows
List some reasons why you would synchronise oestrus?
Can use AI and improve genetic gain
Reduces/confines oestrus detection and labour costs
Shorten calving to conception intervals and increase lactation length
Better management of drying off, transition feeding and claving
Increase number of replacement heifers
Reduce number of bulls needed
Can use ET
List some disadvantages of synchronising oestrus?
Cost
High organisation and skill needed
Appropriate handling and AI facilities needed
Cattle need to be handled repeatedly
Owner’s expectations may be unrealistic
Conception rates can be reduced with some protocols compared to AI
What 6 characteristics would the ideal oestrus synchronisation treatment have?
High response rate when started at any stage of oestrus cycle, including anoestrus
Precise synchrony in time of oestrus and ovulation
Eliminates need to detect behavioural oestrus and enable fixed-time AI
Achieves normal fertility and return to oestrus at repeated services
Economical and simple to implement, with no unacceptable tissue/milk residues
In Norther Aus be of minimum duration and as few handlings as possible
What are the 4 requirement for synchronising oestrus?
Synchronise a decline in plasma concentrations of progesterone and/or exogenous progestogen
Synchronise follicular development
Ensure follicles which ovulate have normal fertility
Ensure concentrations of progesterone following the synchronised oestrus are normal
At the start of a synchronisation protocol where you want to synchronise new wave emergence, how do you do this?
Atresia -Administer oestradiol benzoate in the presence of progesterone (CIDR, Cue-mate) Ovulation -Inject GnRH -Cause surge of LH and FSH
What does treating with progesterone and oestrogen at the same time do?
Get atresia of growing follicles
3-4 days later synchronous new wave emergence
-Progesterone and estrogen = decrease GnRH and atresia
New wave emerges due to increase in FSH
Why do you need to give oestrogen along with progesterone to get atresia of follicles?
When there is low levels of progesterone in the body, estradiol instead has a positive feedback effect on GnRH and the anterior pituitary
-You get growth instead of atresia
How does giving oestrogen and progesterone cause atresia?
Progesterone has a negative feedback on GnRH and LH
Estrogen in the presence of progesterone has a negative effect on GnRH and LH also
Why can’t you just give progesterone over 7 days to synchronise oestrus?
Because continuous high levels of progesterone promote follicle turnover
Since all the cows would be starting this at different stages of follicular growth, then oestrus would also occur variably
How does GnRH administration cause synchronous new wave emergence?
GnRH causes a surge of LH and FSH
This causes ovulation
So therefore either the follicles growing will either ovulate or luteinise
What 2 ways can you synchronise a decline in progesterone?
Inject PGF2alpha
Remove exogenous source of progesterone
What 3 ways can you synchronise a preovulatory LH surge to induce ovulation?
Oestrogen in the absence of P4
GnRH
eCG - less reliable
What 3 purposes does synchronisation of pro-oestrus have?
Improve synchrony of ovulation
Increase probability that ovulation will occur in animals at risk of not ovulating
Enable fixed-time insemination close to expected ovulation time
