Automatic milking system performance: free vs. forced traffic flow

Fernando Diaz

In robotic dairies, cows can move through the pen freely or forced. With free cow traffic, cows decide when to enter the robot whereas with forced cow traffic, the producer set one-way traffic toward the robot by one-way gates or a sorting system in which cows are forced to the milking, feeding, and resting areas.

A recent study published in the Journal of Dairy Science evaluated the characteristics of North American dairy farms using automatic milking systems. Approximately during 18 months, the researchers (Siewert et al., 2019) surveyed 40 dairy farms (39 Holstein and 1 Jersey) with robotic milking systems located in Minnesota and Wisconsin. Thirty-one of the farms used a free-flow cow traffic system (30 Lely and 1 DeLaval) and 9 used forced-flow cow traffic (all DeLaval).

Overall, the researchers observed greater milking frequency in free-flow systems:

  • In multiparous cows, there was no difference in milking frequency between traffic type during the first week after calving (2.56 times/day). From 7 to 298 days in milk (DIM); however, multiparous cows were milked more often in free-flow systems (2.88 x/day) than in forced-flow systems (2.52 x/day). Interestingly, traffic flow system did not alter average milk production during the lactation (33.7 kg/day).
  • In primiparous cows, traffic flow type did not affect milking frequency from 1 to 118 DIM (2.46 x/day). After this period, primiparous cows in free-flow systems tended to have higher milking frequency (2.46 x/day) than cows in forced-flow systems (2.36 x/day). Milk production during the first week of lactation was similar in both traffic settings (14.3 kg/day) but from day 8 to day 118 of lactation, primiparous cows in free-flow system produced, on average, 5.5 kg milk per day more than cows milked in a forced system (29.1 vs. 23.6 kg/day). These results are very interesting because there was no difference between systems in milking frequency during this period.

In conclusion, this study indicates that robotic dairies with free-flow systems showed greater milking frequency. Moreover, in agreement with previous studies, the authors reported that primiparous cows produced more milk in free-flow systems.


M. Siewert, J. A. Salfer, and M. I. Endres. 2019. Milk yield and milking station visits of primiparous versus multiparous cows on automatic milking system farms in the Upper Midwest United States. J. Dairy Sci. 102:3523–3530.

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