Different vacuum levels, vacuum reduction during low milk flow, and different cluster detachment levels affect milking performance and teat condition in dairy cows.

Traditionally, machine milking is performed at a constant vacuum supply. The system vacuum has to be set high enough to allow a sufficiently high vacuum at the teat end, despite the inevitable vacuum drop caused by milk flow. This leads to an increased vacuum load on the teat, especially when milk flow ceases at the end of milking. We tested the hypothesis that a milk flow-controlled adaptation of vacuum settings during milking allows even higher vacuum levels than are usually recommended during the period of high milk flow if the vacuum is reduced during low milk flow. Combined with a high cluster detachment flow rate level, increased milking performance is expected without an increased effect on teat tissue. Ten Holstein dairy cows were milked with a bucket milker with the claw vacuum adjusted in the absence of milk flow at a regular (43 kPa) and high (48 kPa) claw vacuum, with and without vacuum reduction during low milk flow (<2 kg/min), and combined with different cluster detachment levels (0.2, 0.6, and 1 kg/min). Each treatment was applied in each cow during 4 subsequent milkings in a randomized crossover design. Both claw vacuum and milk flow were continuously recorded throughout milking. Teat tissue thickness was measured using a cutimeter and teat wall diameter was measured by B-mode ultrasonography at 5 min after the end of milking. Milk yield was not affected by either vacuum settings or detachment levels. Machine-on time in treatments with vacuum reduction was shorter at high than at low vacuum and decreased with increasing detachment levels. Average milk flow was higher at high than at low vacuum and reached highest values in milkings without vacuum reduction at both vacuum levels. The average milk flow was higher at a cluster detachment of 1 kg/min than at 0.2 kg/min. However, both teat tissue thickness and (as a tendency) teat wall diameter at 5 min after cluster detachment were higher in milkings at high vacuum without vacuum reduction compared with all other treatments. In conclusion, high claw vacuum up to 48 kPa increases milking performance because of higher milk flow and reduced machine-on time. Negative effects of high vacuum on teat tissue are prevented by reducing vacuum during low milk flow (<2 kg/min) at the start and end of milking. Additionally, using a high cluster detachment level reduces machine-on time without a loss of harvested milk.