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:
- The first herd test is within 60 days of calving.
- The interval between herd tests does not exceed 120 days.
- 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