Fear of people by cows and effects on milk yield, behavior, and heart rate at milking.

To examine the ability of cows to recognize people and the effects of the fear of people by cows at milking, cows (n = 14) were handled by two people; one handled the cows gently, and the other handled them aversively. The handlers wore clothes of different color. After handling, the cows stood further from the aversive handler than from the gentle handler. When the handlers changed the color of their clothing, the cows did not discriminate between them. The gentle handler stood close to the cows for one milking, and the aversive handler stood close to the cows for another milking. For two control milkings, neither handler was present. Measurements included milking duration, milk yield, residual milk, heart rates, incidence of movement, and kicking behavior of the cows. Compared with control milkings, the presence of the gentle handler did not change milk yield or residual milk. The presence of the aversive handler increased residual milk by 70%. Kicking behavior of cows during milking was reduced with either handler present, and kicking during udder preparation was reduced with the aversive handler present. For cows that best discriminated between the handlers, the presence of the aversive handler increased movement and heart rate during milking. For cows that did not discriminate well between the handlers, the presence of either handler increased heart rate and decreased movement during milking. Cows recognized individual people, and the fear of people who are present during milking may reduce milk yield.