The maximum number of cows milked per hour depends on the work routine time of the operators.
Work routine includes tasks such as:
- loading the row
- teat washing
- cluster attachment
- cluster removal
- teat sanitisation
- row exiting
- waiting time.
For more detailed information on these tasks, visit the Stockmanship section.
Equation 1: To work out the maximum number of cows able to be milked an hour (throughput), divide 3600 (seconds in an hour) by the work routine time.
The faster the work routine time, the more cows that can be milked an hour.
Limits to achieving the maximum cows milked per hour
How many clusters?
Achieving the maximum number of cows an hour depends on the number of clusters and the milking time of the slowest cow in the row.
If the operator’s work routine takes 24 seconds per cow and the slowest cow in the row takes 8 minutes (480 seconds), dividing 480 by 24 means the operator could efficiently handle 20 clusters.
Equation 2: Optimum number of clusters = milking time of slowest cow (seconds) / WRT (seconds/cow)
(WRT = work routine time)
Using equation 1 this would allow 150 cows/operator/hour.
If the herringbone has 16 clusters, it would take the operator 384 seconds (24 seconds x 16 cows) to complete the routine.
But because the slowest cow is eight minutes (480 seconds), there is 96 seconds of time lost where the operator is idle or waiting.
This extra time has to be added to the work routine, decreasing throughput.
In this case, it would increase the work routine to 30 seconds per cow, reducing the number of cows milked per hour to 120 rather than 150.
Here’s another scenario. If there are 24 clusters, it would take the operator 576 seconds (24 seconds/cow x 24 cows) to complete the routine.
But the slowest cow normally takes 8 minutes (480 seconds) so she is being over-milked by 96 seconds and the rest of the cows in the row are being over-milked even more.
The number of cows milked per hour is still 150, as the work routine means the additional clusters can't be utilised.