Effects of intermittent electrical shock on responses related to milk ejection.

Electrical shock is perceived to be a problem on many dairy farms. Thirteen cows were subjected to intermittent electrical shock (5 s on, 25 s off) at a.m. and p.m. milkings for 7 days. Seven cows were subjected to 3.6 mA shocks starting with preparation (1 min udder wash and dry) and six cows to 6.0 mA. One additional cow initially in the 6.0 mA group had to be removed from the study because of severe behavioral responses to shock. Compared to 5-day preshock and postshock periods, milk yield, milking time, and Wisconsin Mastitis Test scores were not affected by shock. Maximum rate of milk flow increased slightly. The number of behavioral events such as lifting legs during milking increased with a greater increase in the 6.0 mA group. Heart rate was elevated (+3 beats/min) only in response to shock during preparation (initial shock). For selected days, time to peak oxytocin response was delayed in the 3.6 mA group, and peak prolactin and area under prolactin response curves increased similarly for both groups during shock. There were significant a.m.-p.m. differences in milk yield, milking time, maximum rate of milk flow, heart rate, and responses of oxytocin and prolactin. We think that milk yield can be maintained, at least in the short term, in cows subjected to electrical shock due to power-line problems if dairy producers take exceptional care to accommodate behavioral responses.