Cows are social animals that form close bonds with their best friends and become stressed when separated, according to research by Krista McLennan.
Her study, conducted during her PhD at Northampton University, measured heart rates and cortisol levels in cows and found that these bonds could impact milk yields.
Cows were observed being isolated, paired with their best friend, or with an unfamiliar cow, showing they experience less stress when with a close companion.