A breeding ram has only one job. What if he can’t perform? “Unfortunately, he’ll have to go into the food chain,” said Dewi Jones, the chief executive of the sheep-breeding company Innovis, speaking on a Channel 4 documentary, My Gay Dog and Other Animals, which will be broadcast on Thursday. The show reports that one in 12 sheep is gay. “There is ram-on-ram behaviour going on over there,” Jones says, watching his rams. Putting three of the male-oriented rams into a pen with a ewe to see which are interested in her, one uninterested ram is classed as a “shy breeder”. “Commercially, it’s a big issue for us as a breeding company or as a ram breeder because we need our rams to cover lots of ewes.”

Many species – including sheep, penguins, monkeys and dolphins – have been shown to display same-sex preferences. Perhaps the most famous example came to light in 2014, when Benji, a Charolais bull in County Mayo, Ireland, was due to be slaughtered after showing no interest in the heifers he was bought to breed with. Campaigners raised money to send him to a sanctuary instead (although it emerged the following year that he may not be “gay” after all, “judging by what he was trying to do the other day with one of the cows,” said his new owner).

Sex preferences in sheep have been studied by Charles Roselli, a professor of physiology and pharmacology at the Oregon Health & Science University, whose work suggests their sexuality is determined by biology and has said that the research – previously reported by the website Slate under the headline “Brokeback Mutton” – may “allow better selection of rams for breeding and as a consequence may be economically important to the sheep industry”.

“It is reasonably well known that male sheep are influenced by early-life experience and rearing practices which can affect their sexual behaviour,” says Prof Cathy Dwyer, an expert in animal behaviour at Scotland’s Rural College. “There is a study that suggests that about 25% of rams that were kept in an all-male group after weaning were not very interested in ewes when first exposed to them.” However, the study didn’t report if they were interested in males instead, she adds. “We also know that if male lambs are reared by goat nannies they never show an interest in ewes, only female goats. Rams also display broadly similar behaviours towards subordinate males, and male-male mounting is part of play and pre-pubertal behaviour in sheep and lots of other mammals.” Is it a genuine problem for farmers? “I imagine that early rearing with only males would affect initial encounters with ewes, which might not be ideal for farmers,” she says. “If the animal was not dominant, that might persist.”

Phil Stocker, the chief executive of the National Sheep Association, hasn’t heard of rams – or bulls – being sent to the slaughterhouse for showing exclusively same-sex preferences. “I can believe that a lot of rams and bulls show interest in each other, but that’s not to the exclusion of them showing an interest in females,” he says. “Usually, the ones with the stronger sex drive are just as interested in males as they are in females. They’ve either got no sex drive or a very high sex drive.”

This is played out on farms across the country. “You often get rams who sniff and ride other rams. Usually that would be at the time of year when ewes are coming into season and their sex drive is starting to increase; they will ride anything. You see that in bulls and even in steers [castrated cattle]. When they smell [females] coming into season, they will ride other cows.” But he adds: “This is not an issue at all, commercially.”