Research strategy

Cattle were monitored monthly in the present study. Thus, a unit of time could be defined as little as one month.

However, the resulting statistical model is likely to be highly complex and will need to take into account seasonal variations, changing ages of cattle, changes in physiological status, such as pregnancy and lactation, serial correlations between successive measurements, and so on.

Simpler models based on wider time units over which the different performance variables can be summarised are easier to analyse and interpret.

In the present study it was decided to define 6-month time intervals over which data would be summarised. These intervals would match wet and dry seasons, respectively.