A researcher from the University of Northampton has been finding out if cows get lonely.
Krista McLennan, a doctoral student, wanted to find the effects of isolation on heifers.
"We've looked at heart rates during social isolation and also measured their cortisol levels which is a potential stress indicator in animals," she said.
The cows' stress levels were tested in different environments.
Cattle were held in an isolation arena for 30 minutes and their heart rates were measured at 15-second intervals.
"It's important for the dairy industry to reduce stress levels within cows but also to try to help farmers reduce the impact on their milk yield," said Ms McLennan.
The research also helps to find out if cattle have a preferred partner while producing milk and seeing if farmers can find other ways to increase their production.
Ms McLennan said: "When heifers have their preferred partner with them, their stress levels in terms of their heart rates are reduced compared with if they were with a random individual."
Charles Reader, from Cloisters Farm, a farmer at Evenley village near Brackley for 28 years, said: "All livestock are herd animals and they get a bit stressed if you separate them out."