Cows Stress When Separated

Krista McLennan, a PhD student at Northampton University in the United Kingdom, found that cows strongly connect with certain members of their herd, and become stressed when separated from them. Heart rates and levels of cortisol—a stress hormone—in the cows’ blood were measured when the cow was penned alone, with his or her “best friend,” or with an unknown cow; stress levels were reduced when the cow was paired with his or her preferred partner. Thousands of cows in the US are held on factory farms, where they are often confined in cramped and highly stressful quarters.