Milking cows with positive pressure stimulation in late lactation

Twelve Holstein cows in second halves of lactations were divided into two groups of six each, designated "unstimulated" and "stimulated" groups. Over a preliminary 11 days, all cows were stimulated before each milking by a 1-min hand wash. After this period, premilking preparation and stimulation routines were changed for both groups. The "unstimulated" group was changed to a milking routine that included no premilking udder stimulation. The "stimulated" group was treated for the 1st min after cup application with positive pressure (raising pressure at the pulsator's air vent to about 80 kPa above atmospheric). Both groups of cows were milked twice daily by these two routines for 56 days. "Stimulated" cows showed no significant difference of milk production compared with cows given no premilking udder stimulation. Both average fat percent and milk fat yield was greater for cows given positive pressure than for those receiving no premilking stimulation. Cows given positive pressure stimulation did not differ significantly in protein percentage or production from unstimulated cows, nor did positive pressure stimulation affect machine-on time, residual milk yield, or prolactin or cortisol release. Cows given positive pressure stimulation showed a more rapid rise of concentrations of oxytocin in serum than cows given no stimulation.