17.4.5: Fertility data analysis Flashcards
This is closely linked with '17.4.2: Infertility in the herd'
What are submission rates and what do they tell us?
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.
What are some sensible targets for submission rates?
80% for first serve
60% for returns
What is a normal inter-service interval?
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
What is the ‘pregnancy per unit time’ approach to monitoring fertility?
- 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
What are some reasonable targets for a year round calving herd for:
a) serve rate
b) 21d pregnancy rate
a) Serve rate: >65%
b) 21 day pregnancy rate >20-25%
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
Hierarchy is as follows.
21d pregnancy rate = fertility efficiency
What parameter should you start with when assessing fertility? Why?
- 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.
Fertility efficiency in a given herd is low (i.e. poor 21d pregnancy rate). What 2 areas do you now need to examine?
- Insemination rate (i.e. are they detecting and serving cows?)
- Conception rate (i.e. are the cows becoming pregnant when served?)
Conception rate
proportion of serves that lead to a pregnancy
Insemination/submission rate
proportion of eligible cows that are served in a given time period.
A cow has just finished the voluntary wait period. When do you want her to have her first serve?
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.
What is the difference between fertility efficiency (21d preg rate) and conception rate?
- 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)
Pregnancy rate
proportion of serves leading to pregnancy.
What might your target calving index be in an all-year round calving herd?
370-375 days
(This is harder to achieve in higher yielding herds).
Fertility efficiency
Proportion of eligible cows becoming pregnant every 21d