The study showed that ewes fall in love with rams, have best friends and feel desolate when those close to them die or are sent for slaughter. The discovery could have important implications for the way farm animals are treated.

Such issues will be addressed in detail this week at a conference on animal sentience to be held in London by Compassion in World Farming.

Professor Keith Kendrick, the neuroscientist at the government’s Babraham Research Institute in Cambridge who led the research, said sheep and human brains had a startling amount in common.

In the research, Kendrick first inserted tiny electrodes into the brains of sheep to measure how electrical activity varied when they were offered stimuli. These included being shown pictures of rams with which they had been closely associated or ewes that were among their group of “friends”.

Kendrick and his colleagues recorded the changes in electrical activity and observed the animals’ behaviour while they were being shown such pictures. In other experiments the animals were painlessly killed after exposure to the pictures. Then their brain cells were studied to see how levels of certain chemicals had changed.

Studies in humans have used magnetic resonance imaging to measure how different parts of the brain become activated when people are shown images of their loved ones. Kendrick found that the electrical activity and chemical responses in sheep were very similar.

Kendrick says it is clear that female sheep actively solicit and enjoy sex — and may even have orgasms. But the study shows ewes forget about their lovers far more quickly than women.

It is not the first time sheep love has been reported. Woody Allen portrayed a love affair between a doctor, played by Gene Wilder, and a sheep called Daisy in the film Everything You Always Wanted to Know About Sex But Were Afraid to Ask.

Donald Broom, professor of animal welfare at Cambridge University, believes animals living in herds can devise their own “moral codes”. “Just watching them we can see how they are often friendly and altruistic towards each other,” he said.

Joyce d’Silva, director of Compassion in World Farming, said: “People have long acknowledged that their pets have personalities and complex emotions and would never tolerate them being treated as badly as we treat our farm animals. It’s time to rethink that.”

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