Production data was imported from the IndividualRAM (NorFor) database. The production value (ECM, energy corrected milk) from one month before, one month after and from the actual month the tests were carried out were incorporated in the statistical analysis in order to investigate if current lactation status influenced cow behaviour.

Since cows differed in age, lactation, month of pregnancy and months since last calving, the production values used in the statistical analysis were total amount of milk (kg), percent of fat (%) and protein (%) and total amount of ECM (kg) from the five first test milkings (one per month) during the individual cows’ first, second and third lactation. Thus, this was a comparable measure of milk production across cows, independent of their current somewhat varied status.

Each individual cows’ production parameters (kg, fat, protein and ECM) from first, second and third lactation were plotted, and ‘a’ obtain from a linear function (y = ax + b) of the individual cows’ increase in each value respectively were calculated. The value of increase (‘a’) on each production parameter (kg, fat, protein and ECM) was used to get a measurement of milk production as a life-history trait, thought to capture any variation in production ‘style’ of individual cows, in other words whether cows produced more or less milk earlier in life.