Study design

The design of the main longitudinal study is described in Romney et al. (2005). The concept of the study was presented in early 1999 to a meeting of farmers. Ninety farmers with cows due to calve between April and July 1999 volunteered to participate in the study and alter their feeding practices by reallocating their concentrate feeding to early lactation. Sixty from the 90 farmers were selected at random for the study. Another 30 farmers who did not wish to alter their feeding practices agreed to be monitored as controls.

The concentrate feeding management offered to the farmers was based on the earlier experimental findings, in other words to reallocate the concentrate they buy to the first 12 weeks of lactation.

However, there was no attempt to insist that the farmers followed exactly the instructions provided by the researchers. Instead, the researchers were interested in seeing how farmers put the instructions into practice. Frequency of monitoring was planned to be weekly for the first 12 weeks of lactation and fortnightly thereafter.