Effect of dynamic pulsation and milk flow rate switch-point settings on milking duration and postmilking teat condition

The objective of this study was to investigate the effect on milking duration and teat condition after milking with dynamic pulsation settings that increased the open phase and reduced the closed phase of pulsation during the peak milk flow period, together with increasing the milk flow rate switch-point for cluster detachment. The present study filled current gaps in knowledge by informing on the effects of both milk flow rate switch-points and dynamic pulsation together in one experiment, along with presenting data on milking performance, strip milk, teat condition and vacuum levels in the cluster during milking. To this end, 4 treatments consisting of different milk flow rate switch-points and pulsator settings combinations were deployed across 4 groups of 24 cows for 8 weeks. Treatments consisted of 2 levels of milk flow rate switch-point (0.2 kg/min and 0.8 kg/min) and 2 pulsator settings (static and dynamic). The static pulsator settings had a pulsator ratio of 65:35. For the dynamic settings, a pulsator ratio of 63:37 below a milk flow rate of 2 kg/min was used, which changed to 73:27 above 2 kg/min. Milking parameters and teat scoring data were analyzed using mixed models. The effect of milk flow rate switch-point on milking duration was significant, whereas the effect of dynamic pulsation was not. The reductions in milking duration were larger for p.m. milking (for static pulsation settings, the average reduction was 21% between switch-point of 0.2 kg/min and 0.8 kg/min) compared with a 12% reduction for a.m. milking. In addition, we found a significant effect of treatment on teat-barrel congestion, with reduced odds of teat-barrel ringing for treatments with a milk flow rate switch-point of 0.8 kg/min relative to 0.2 kg/min due to significantly reduced over milking time and hence reduced exposure to higher mouthpiece chamber vacuum during the over milking period. On average across all treatments, cows spent 32% of the milking above 2 kg/min, but this varied from 37% for a.m. milking to 23% on average for p.m. milking; hence, an uneven milking interval impeded the ability of dynamic pulsation to contribute, especially for p.m. milking. We concluded that milk flow rate switch-point settings are more impactful than dynamic pulsation settings for reducing milking duration. Furthermore, we found no evidence of interactions between the effects of switch-point and pulsator setting on milking duration, milk yield or milk flow rate.