Effects of Duration of Udder Stimulation on Milking Dynamics and Oxytocin Release

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Abstract
For effects of varying duration of premilking manual udder massage on milking performance and oxytocin release, 5 Holstein cows were subjected to no stimulation, stimulation by manual udder massage before machine attachment for 15 s, for 30 s, for 60 s and for 120 s. Milk yields, fat, protein, and somatic cell content were not affected by treatments. The 30, 60 and 120 s treatments resulted in higher peak milk flow rate as compared to no stimulation. Stimulation for 60 or 120 s did not achieve higher peak milk flow rates than 15 or 30 s. Average milk flow rate increased with duration of stimulation, and no stimulation differed from 30, 60 and 120 treatments. Machine-on time decreased with increasing stimulation. Differences in average flow rates and machine-on times became nonsignificant when premilking stimulation time was added to machine-on time. No differences were significant between treatments and mean oxytocin concentrations. The marked difference in milk flow variables and machine-on time suggested that a small yet finite threshold concentration of oxytocin led to milk ejection. Udder massage of 30 s prior to machine attachment was more than adequate for preparing cows for milking with machine stripping.