Feel like telling your dairy cow to get a life? Don't bother, it already has one - a social life that should not be ignored if you want to minimize stress and maximize milk output, a Utah State University professor said.

A "pecking order" among dairy cows affects stress and milk production, said Clive W. Arave, associate professor with the animal, dairy and veterinary sciences department.Speaking Friday during a Cooperative Extension dairy teleconference sponsored in part by USU and broadcast to six locations statewide, Arave said cows grouped together establish dominance within a few minutes of initial contact. This is initiated by aggression or threat, although true fights are rare.

Often a head gesture or threat is enough. Once dominance is established, memory of previous encounters serves to keep aggressive behavior to a minimum, he said.

The dominance is correlated with age, size and horns. Arave said older cows tend to dominate younger ones, mothers dominate daughters, larger cows control smaller ones, and an animal with horns will generally dominate a polled cow. Breed differences also have been found to affect dominance relationships.

He said problems come when cows are switched from group to group. Cows are often grouped for age, production, or reproductive reasons.

Milk losses of zero to 10 percent may occur the first few days after switching groups, he said.

"Since this represents an average, individual cows may drop in yield more, others less," he said. "The social hierarchy is established within a very few days of switching."

When cows must be switched from one group to another, Arave said, farmers can do some basic things to minimize trauma:

- Divide up as many production groups as practical.

- Make sure groups do not exceed 100 cows. The optimum number is 50 to 60 for maximum social stability.

- Minimize moves. Cows should not be switched more than once a month.

- Move cows in groups. Cows should be moved together rather than individually if possible. They should also be moved at times of high activity, such as feeding or moving to and from milk parlors.