17.4.5: Fertility data analysis

Question 1

What are submission rates and what do they tell us?

Answer 1

Submission rates: can include both first serve and return to serve.
* Tells us what % of heats are being detected.
* Does not tell us if the cow is being served soon or too long after target -> we need additional interval data for that.

Question 2

What are some sensible targets for submission rates?

Answer 2

80% for first serve
60% for returns

Question 3

What is a normal inter-service interval?

Answer 3

18-24 days
This indicates normal return and correct oestrus detection.

NB: Remnant argues intervals of 25-26 days are very common and could be normal

Question 4

What is the ‘pregnancy per unit time’ approach to monitoring fertility?

Answer 4

• Look at total number of cows in the herd
• Remove those that are in calf/too early to serve
• This leaves the eligible population remaining i.e. who you should serve in a given time
• Then see how many of these get served
• Then see how many of these fall pregnant

Question 5

What are some reasonable targets for a year round calving herd for:
a) serve rate
b) 21d pregnancy rate

Answer 5

a) Serve rate: >65%
b) 21 day pregnancy rate >20-25%

Question 6

Rank the following parameters from most to least important in terms of monitoring fertility
* Insemination rate
* First serves - rates and intervals
* Returns - rates and intervals
* Conception rate
* 21d pregnancy rate

Answer 6

Hierarchy is as follows.
21d pregnancy rate = fertility efficiency

Question 7

What parameter should you start with when assessing fertility? Why?

Answer 7

• Start with overall 21d pregnancy rate (=fertility efficiency).
• This tells you how well the farm converts a non-pregnant eligible cow to a pregnant cow.
• If this is OK (25% all the time) then fertility will be working well and you don’t need to make further investigations.

Question 8

Fertility efficiency in a given herd is low (i.e. poor 21d pregnancy rate). What 2 areas do you now need to examine?

Answer 8

• Insemination rate (i.e. are they detecting and serving cows?)
• Conception rate (i.e. are the cows becoming pregnant when served?)

Question 9

Conception rate

Answer 9

proportion of serves that lead to a pregnancy

Question 10

Insemination/submission rate

Answer 10

proportion of eligible cows that are served in a given time period.

Question 11

A cow has just finished the voluntary wait period. When do you want her to have her first serve?

Answer 11

Within the first 24 days after the end of the voluntary wait period. This should theoretically encompass the whole of the cow’s cycle.

This period is shown by the green box on the graph.

Question 12

What is the difference between fertility efficiency (21d preg rate) and conception rate?

Answer 12

• 21 d preg rate is proportion of eligible cows that end up pregnant (=pregnant/eligible to get pregnant)
• Conception rate is proportion of served cows that end up pregnant (=pregnant/was actually served)

Question 13

Pregnancy rate

Answer 13

proportion of serves leading to pregnancy.

Question 14

What might your target calving index be in an all-year round calving herd?

Answer 14

370-375 days
(This is harder to achieve in higher yielding herds).

Question 15

Fertility efficiency

Answer 15

Proportion of eligible cows becoming pregnant every 21d

Question 16

First serve submission rate

Answer 16

proportion of cows getting first serve within the first 24d of becoming eligible.

Question 17

DIM at first serve

Answer 17

Number of days from calving to first service for each cow - can be presented as a distribution, or median/mean calculated

Question 18

Returns submission rate

Answer 18

Proportion of heats detected at first opportunity in cows “returning” to heat after an unsuccessful serve.

Question 19

Inter-service interval

Answer 19

Interval between successive serves for the same cow - usually compared to “normal” interval of 18-24 days.

Question 20

What kind of output would you expect from a high output herd?

Answer 20

10-11,000 litres/cow/year

Question 21

Wht might your target for conception rate be? Compare AYR high output herds to block calving, low output herds.

Answer 21

Conception rate: (a.k.a. pregnancy rate) proportion of serves resulting in pregnancy.
* AYR high output >35%
* AYR low-medium output >40%
* Block calving low output >55%

NB: target figures should be provided in exams.

Question 22

What might your target for fertility efficiency be? Compare AYR high output herds to block calving low output herds.

Answer 22

Fertility efficiency: (a.k.a. 21d pregnancy rate) proportion of cows becoming pregnant every 21 days.
* AYR high output >17-20%
* AYR medium-low output >20%
* Block calving low output >50%

NB: target figures should be provided in exams.

Question 23

What might your target for first serve submission rate be? Compare AYR high output herds to block calving low output herds.

Answer 23

First serve submission rate: proportion of cows getting first serve within first 24d of becoming eligible.
* AYR high output >70%
* AYR low-medium output >70%
* Block calving low output >95%

NB: target figures should be provided in exams.

Question 24

What might your target incidence of abortion be?

Answer 24

Abortion incidence: abortions per 100 cows per year OR % of pregnancies aborted.

Target <3-5%

Question 25

This graph shows inter-service intervals. If you have a number of cows falling into column 1, what might this suggest?

Answer 25

• Column 1 = 0-17 days
• This is less than the normal oestrus cycle for the cow
• This might suggest short return to oestrus, follicular cyst, or (esp if a number of cows) inaccurate heat detection i.e. the cow being served when she is not in oestrus. Consider whether an automated system may be generating false heat notifications.

Question 26

This graph shows inter-service intervals. If you have a number of cows falling into column 2, what might this suggest?

Answer 26

• Column 2 = 18-24 days
• This in the length of the normal oestrus cycle
• This indicates normal return to oestrus, and correct heat detection

Question 27

This graph shows inter-service intervals. If you have a number of cows falling into column 3, what might this suggest?

Answer 27

• Column 3 = 25-35 days
• Remnant’s research found that in many cows, 25-26 day cycles are normal, so might be worth investigating a further breakdown of this column and seeing how many cows could fall into this potentially ‘normal’ group
• A high proportion of cows in this group (that do not fit Remnant intervals) might suggest abnormal return, inaccurate heat detection, or late embryonic death

Question 28

This graph shows inter-service intervals. If you have a number of cows falling into column 4, what might this suggest?

Answer 28

• Column 4 = 36-48 days
• This is twice the length of the normal oestrus cycle in the cow
• This indicates a normal return after a missed heat

Question 29

This graph shows inter-service intervals. If you have a number of cows falling into column 5, what might this suggest?

Answer 29

• Column 5 = 49+ days
• This is a very long time to go between services
• This indicates multiple missed heats or foetal death

Question 30

How should we ideally measure pregnancy rate?

Answer 30

Pregnancy rate: proportion of serves leading to pregnancy.
* Outcome ideally via PD.
* Can also use non-return to serve (although this doesn’t guarantee she is pregnant) or next calving

Question 31

True/false: monitoring calving index and culling rates for fertility reasons is an appropriate way to monitor fertility on-farm and ascertain where the root cause of any problems is.

Answer 31

False
* Monitoring calving index and culling will make us very slow to respond to changes (it takes months to see what has gone wrong)
* This also doesn’t show where the problem is (i.e. is it detecting heat? Serving cows at appropriate time? Embryonic loss? etc.)

Question 32

What factor is likely to be top of your list for a poor conception rate? What could be some other factors responsible for this?

Answer 32

Top of ddx list: Negative energy balance

Other factors:
* Nutrition: micronutrients, SARA, excess protein
* AI related: technique, semen quality, semen storage, thawing and handling, timing of AI
* Disease: lameness, herd level infectious disease (IBR, BVD, Lepto), uterine bacterial disease, venereal disease (e.g. Campylobacter)
* Bull: true infertility, lameness, lack of libido

Question 33

What are your thoughts on this herd’s calving index?
They are a 100-cow herd with a 7000 litre/cow 305d milk yield.

Answer 33

460 days is too long!
The target for this herd would be ~370 days as they are a medium-yielding AYR herd.

Question 34

What are your thoughts on this herd’s first service submission rate? What about their conception rate?
They are a 100-cow herd with a 7000 litre/cow 305d milk yield.

Answer 34

• First service submission rate is poor - target for this herd is >70%, but they are achieving 27.3% at best. They are missing the first opportunity to serve many cows after the voluntary wait period.
• Conception rate is OK - target for this herd is >40%, and they alternate above and below this. They might be serving cows at the appropriate time (i.e. when they do serve a cow, she is definitely in oestrus) OR perhaps they are failing to record services and therefore falsely raising their conception rate.

Question 35

What are your thoughts on this herd’s first service timing? They are a 100-cow herd with a 7000-litre/cow 305d milk yield.

Answer 35

• Ideally, every cow should fall within the green box.
• This herd are not managing this at all.
• They are also failing to catch cows quickly (i.e. in the 24 days) after this - one cow didn’t receive her first serve until 150 days post-calving (this is insane).

Question 36

A herd have identified that their heat detection is poor. They are not able to hire more staff to watch the cows for signs of oestrus, and do not have the budget to invest in expensive monitoring technology. What interventions could you suggest to help them improve?

Answer 36

How to cheaply improve heat detection
* Put Kamars (see image) on every cow who is 40 days post-calving (may adjust days depending on the farms voluntary wait period)
* Put tail chalk on every cow that was last seen bulling 10-17 days ago as she is expected to come bulling again soon
* These interventions (Kamars and tail chalk) are cheap. They do not require much time to implement (can put them on when cows are in the parlour)
* This does not require farm staff to spend more time watching the cows so is good for the farm where staff may be time-poor