Calves who were stroked by people early in their life gained weight more quickly than animals that were not stroked, according to researchers at the Vetmeduni Vienna in Austria.
Researcher Stephanie Lürzel said this knowledge could be of commercial value for farmers, as cows produced more milk if they had a higher weight gain as calves.
She studied 104 Holstein calves at a commercial dairy farm in eastern Germany.
Around half of the animals were stroked on the lower part of the neck for three minutes a day for a period of 14 days after their birth, whereas the other half was not.
Ms Lürzel said about 90 days after their birth, stroked calves weighed about 3 percent higher than that of the control group.
She said this would translate into around 50 kilograms more milk per cow per year.
Based on that number, if all the dairy farmers in New Zealand patted their calves for three minutes per day then milk production could be increased by 250 million kilograms of milk per annum.