Accumulated lactation and days in milk

The accumulated lactation of an animal provides an accurate estimate of production over a season.

This is calculated by multiplying production data from herd tests over the season with days in milk.


We often get questions querying the days in milk and why they may appear to be less in our accumulated lactation calculation.

For all days in milk to be included in the accumulated lactation calculation, the herd test dates must align with these conditions:

  1. The first herd test is within 60 days of calving.
  2. The interval between herd tests does not exceed 120 days.
  3. The last herd test is no earlier than 15 days before the end of lactation.

Days in milk that fall outside of these conditions are not used when calculating the animal’s accumulated lactation.



The total number of days in milk between calving and the dry-off date for the animal in the table below was 263 days. However, as the first herd test was 95 days from calving (instead of the recommended 60 days), 35 days in milk was subtracted, meaning only 228 days will be used to calculate the cow’s accumulated lactation.

263 days in milk – 35 days (days in milk that fall outside of conditions) = 228

Accumulated lactation


Days in between


Dates 15/08/2020

1st test

Dates 18/11/2020

Days in between 95

2nd test

Dates 05/02/2021

Days in between 79

3rd test

Dates 25/04/2021

Days in between 79

Dry off

Dates 05/05/2021

Days in between 10

Frequently asked questions

Why are my days in milk lower than expected?

Days in milk that fall outside of our recommended conditions are excluded when calculating an animal’s accumulated lactation figures.

How can I see total number of days my animals have physically lactated?

This information is in MINDA® LIVE, by adding the ‘Days Lactating’ attribute to either groups or reports. This shows how many days the cow has been physically in milk for.

Will a loss of days in milk affect an animal’s indexes (BW, PW, LW)?

No, only test day information is used for animal evaluation.