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
What can cause the onset of oestrus and ovulation to vary?
Maturity of growing follicles at time of luteolysis
Decline in P4 concentrations
-This can be overcome by inducing ovulation
How can you ensure to ovulate an oocyte with optimum fertility?
By restricting the duration of dominant to 4 days by limiting length of P4 to 7-10days
What happens if you try and force ovulate a follicle that is too small?
You will get decreased fertility
-It either won’t ovulate or it will but produce less P4
What happens if you try and delay ovulation to let the rest of the herd to catch up in the cycle?
The persistent dominant follicle will lead to an aged oocyte which decreases fertility
What is the aim of a PG program to do?
PGF2alpha / analogue are adminstered to cause luteolysis
This synchronises a decline in plasma concentrations of progesterone
Which initiates the follicular phase
What day of the cycle is PG effective?
Days 7-18 in cows
-The CL needs to be over 5 days old
What part of the cycle won’t PGF2alpha be effective?
Early dioestrus won’t undergo luteolysis
If in follicular phase won’t have a CL
What are some advantages of a PG program?
Easy to administer - IM injection
Variety of treatment programs can be used to tailor to needs
Normal fertility
Economical - $2-3
What are some disadvantages of a PG program?
Only animals with a CL of appropriate age will respond
Ineffective in anoestrous cows
Ineffective in cows that are already undergoing luteolysis
Can cause abortion if pregnancy under 5 months
Health and safety issues
Wide pattern of onset of oestrus, spread over 5-7 days
From injection of PGF2alpha to oestrus, what will be the order in a cow; with a dominant follicle undergoing atresia, mature follicle, and an immature follicle
Mature follicle first
Next immature follicle
Last is dominant follicle undergoing atresia
In a ‘one shot’ PG protocol, how much of the herd should theoretically respond?
2/3rd’s
-66%
What does oestradiol benzoate do?
Induces oestrous behaviour and preovulatory surge of LH
Get ovulation 40-60 hours after
What does GnRH do?
Causes ovulation or luteinisation of dominant follicles over 10 mm
Get ovulation 24-34 hours after
What is luteinisation?
Formation of a corpus luteum
What are two prostaglandins that are available for use?
Cloprostenol
Dinoprost
Describe a one shot PG protocol?
Day 0 - 7 oestrus detection and AI those in oestrus
Day 5-7 Inject those which have not come into oestrus with PG
-The rest should now come into heat over the next few days, AI when detected
Describe a two dose PG protocol?
Day 0 Inject all with PG
+/- detection of oestrus and AI
Day 11-14 Second injection of all cows with PG
Then as they are detected in oestrus, AI them
How does a two dose PG protocol work?
For PG to work the CL needs to be of a certain age
For the first shot, not all of the cows will have a responsive CL
For those that do, it will cause luteolysis and new wave emergence
Therefore by the second injection, almost all cows will have a responsive CL and respond to treatment
This syncs the oestrus cycles and only need to detect oestrus over a few days instead of 3 weeks
Why do you still need to detect oestrus before AI when using a PG protocol?
Because ovulation is variable when using this type of program
Can come into estrus normally between 2-5 days
How do progestogen based systems for synchronising estrus work?
Increase circulating concentrations of progesterone/progestogen to act as an artificial CL
How can you remove the endogenous source of P4 before inserting an intravaginal progesterone device?
By giving a luteolytic
-Gets rid of the CL so no progesterone produced naturally
What phase of the cycle should a cow move into after removing a cue-mate or CIDR device?
Follicular phase
-Decline in P4
Will the use of a CIDR/cue mate device be effective to induce oestrus in a cow that is anoestrous?
Yes
What is MGA?
Orally active progestogen that can be put into feed
- Not available in Aus
- Given for 2 weeks
What are some advantages of a GnRH based protocol?
Simple
Some effect in non-cycling cows
Intermediate cost
More applicable where heat detection is a problem
What are some disadvantages of a GnRH based protocol?
Conception rates can be low
Proportion of cows showing heat is reduced
Not recommended for heifers
What do you need to do before using a GnRH based protocol?
Presynch
-So that there is a higher chance of ovulation following administration of GnRH on day 0
What are some strategies to presynch before using ovsynch or other GnRH protocols?
2 injections of PG at 14 day intervals then doing Ovsynch 14 days later
Injecting PG and heat detecting with AI for 3 days, then starting protocol with GnRH injection
Double Ovsynch
What can be given at the end of an Ovsynch treatment to increase pregnancy rates?
2 shots of PG am and pm
seven days after injecting GnRH
What are some indications for using Ovsynch?
Poor heat detection
Reluctance to practice continuous heat detection
Simple reproductive program
What is the conception rate?
% of oocytes during oestrus that are fertilised and develop into a zygote after fertilisaiton
What is the typical conception rate range?
30-60%
What is the non-return rate?
% of animals not detected in oestrus after insemination
Will the non-return rate or pregnancy rate be higher?
Non-return rate
-Some cows won’t return to oestrus even if not pregnant
When would you use non-return rate data rather than pregnancy rate data?
When you can’t pregnancy test but you do have info on rates of return to oestrus
Where should you position the AI gun when inseminating?
Just through the cervix
-The uterus is only a few cm’s deep and don’t want an unequal distribution
In licensed semen centres, what 12 diseases do bulls must be free from?
Enzootic Bovin Leucosis Infectious Bovine Rhinotracheitis Tuberculosis Brucellosis Johne's disease Trichomoniasis Leptospirosis Ephemeral fever BVD Q fever Campylobacteriosis Blue tongue
What are the 2 most common methods of semen collection in a bull?
Artificial vagina
Electroejaculation
How frequent can a bull be collected from?
3 times a week
Which is up to twice a day, 3 days a week
What is the average volume of ejaculate?
4mL
What is the average number of sperm per ejaculate?
1/2 to 4 billion
How many AI doses can you get per ejaculate?
50 - 200
How many sperm are in each AI dose?
10 x 10^6 progressively motile and normal sperm
Post thawing how many sperm should be alive and progressively motile?
30% should be alive
With 30% of those progressively motile
After detecting oestrus, when should AI be done?
4-14 hours post onset
If the exact onset of oestrus is not known, what recommendation should you give to a farmer of when they detect a cow in oestrus?
Straight away
-Don’t know how long she has been in oestrus for
What temperature does frozen semen need to be stored at?
-100 degrees
