Researcher Stephanie Lurzel says 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.
Lurzel says about 90 days after their birth, stroked calves weighed about 3% higher than that of the control group.
She says this would translate into around 50kg 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 kgMS per annum.
