• Download and open the spreadsheet from the above link
• Select either 'herringbone' or 'rotary' from the sheet tabs across the bottom.
• Enter your farm details in the dark grey boxes (herd size, shed size etc).
  Note: you may need to click “enable editing” in the yellow ribbon across the top of the window.
• All the dark grey boxes in the left hand column must be filled in.
  Note: roll the mouse over the cell (red triangle) for a more detailed explanation of each box.
• Select the post-milking strategy you use at each milking. See our content on Herringbone and Rotary systems.
• The light grey boxes in the middle and right hand columns are a prediction of key measures for the morning and afternoon milkings; particularly focus on the cows/operator/hr which determines the total labour hours.

• Do a quick logic check of the results – are there any impossible results e.g. a herd milking duration of 10 hours. If there are problems, check back to the input boxes. Note that the number of operators is predicted by the model and cannot be entered.
• In the herringbone, the model estimates a cow milking time based on the milk yield for each milking as determined by what has been entered in box c) and d). It them compares the time it will take for an operator to complete the tasks, as determined by boxes b) and e). If this time is greater than the milking duration of the slower cows, then it assumes a second operator is required. If you believe the model is overestimating the number of operators then this indicates you may be over-milking cows, or you can adjust the core work routine down until you get the desired result.
• In the rotary, the model first estimates a cow milking time based on the milk yield for each milking as determined by what has been entered in boxes c) and d). It then estimates the number of cows that would require a second rotation by comparing the milking time and the rotation time entered (h) – unless MaxT has been selected as the end-of-milking strategy, in which case it assumes no cows go on a second rotation. Using the rotation time the number of go-around cows and the number of bails (b) it calculates the time available per cow to attach clusters. If the time available is less than entered in (e) then the calculator assumes a second cups one person is needed. Similarly, if manual cluster removal is selected an additional operator is added for the cups-off position.
• The model determines a maximum potential given the values that have been entered, so it is likely that your actual performance will be slightly lower. If the actual performance is well below what the model has predicted then it is possible that poor cow flow may be reducing efficiency.  See the design pages or Milking Smarter workbook for herringbones to help diagnose problems.
• The model determines a maximum potential given the values that have been entered, so it is likely that actual performance will be lower, however this will affect all scenarios you enter equally so the calculator is an effective way of comparing the likely performance of different dairy setups and management decisions.

In a herringbone, if the model has estimated there is significant idle time, look to see how many operators it has calculated is required. If the number of operators are what you’d expect then try changing the post milking strategy, using MaxT will normally reduce idle time. Alternatively, it means more clusters can be handled. If there are more operators than you believe are required then try adjusting the number of clusters down, or it means that a faster work routine is required. This may mean additional technology, e.g. an automatic teat sprayer, is required to remove a task from the work routine.

Applying MaxT or increasing the ACR threshold will help reduce idle time.

Note that for MaxT in the herringbone the model assumes that the slowest 20% of cows will have milkings shortened. This may result in another operator being added, when in practice, it is normally not required because it also shortens the work routine as well so adjust this value down to remove the additional operator.

In the rotary, if using ACRs, then select a rotation time where about 15-20% of cows are going-around. However, then check the number of operators required. If reducing the rotation time has meant an additional cupper is required then consider whether cupping technique can be improved (reduce box e), or increase the rotation time slightly – as it is unlikely the increase in throughput will justify adding another person at cups on.

In the rotary, if selecting MaxT as an end-of-milking criteria then select a rotation time where 20% of cows will have their milkings shortened e.g. not allowed to go-around on a second rotation. The number will turn red if greater than 20%. As with the previous example, it may make sense to use a rotation time where less than 20% of the cows are truncated if it avoids needing another operator (for example at the afternoon milking).

Compare the total number of labour hours in each scenario you try.