AS MANY as one in 12 rams are born with a 'same sex preference' that makes them useless to commercial sheep businesses.

This surprise statistic was aired on a Channel 4 documentary last weekend – 'My gay dog and other animals' – that looked at the phenomenon of same sex preference in a variety of mammals, from the aforementioned pet dog, to wild lions and monkeys, and in particular, sheep.

Dewi Jones, chief executive of Wales-based commercial sheep breeder Innovis, acknowledged that the sheep sector was well aware that a certain proportion of rams would be classed as 'shy breeders', but conceded that the term was something of a euphemism, because some of them were anything but shy when it came to other rams.

"Ram-on-ram action is well-known on sheep farms, but so long as they also mate with ewes, it is not a problem," said Mr Jones. "But we find that 8% of any of our ram flocks can be totally male-orientated – one in 12 rams. That has serious implications for a commercial flock."

Mr Jones revealed the inspection procedure for prospective working rams, and in particular, how Innovis dealt with young tups that showed regular interest in their peers. As a first test, he put three rams that had shown mounting behaviour to each other in a pen with a ewe, and noted that two of the rams then showed similar interest in the female, and could therefore be expected to perform commercially – but one of the males showed no interest at all and drifted off to sniff at males in adjoining pens.

As a final test, that disinterested tup was then put into a pen with no less than 30 in-season ewes, where he once again showed no interest in mating. Mr Jones said that his company could not in good faith sell that tup on to a commercial farmer, who would expect it to mate with 30 to 40 ewes in a two week period – and admitted “he’ll have to go into the food chain."

Professor Charles Roselli of the Oregon Health and Science University, Portland, commented that his research on sheep brains had shown differences in one area that was enlarged in those tups with opposite sex interest, but half the size in those males that preferred same sex interactions, and suggested that the roots of sexual preference could be traced to pre-natal development, and explain same-sex mating wherever it occurred in nature.

However, parallel research in the UK at Imperial College, London concluded that there was nothing as simple as a single 'gay gene' in animals, and that the phenomenon was the product of a complex interaction of factors. In particular, researchers suggested an evolutionary advantage in the associated genes, in that the close female relatives of 'gay' animals might benefit from being be 'hyper feminine' and therefore be more successful at attracting mates and continuing their bloodline.

Commenting on behalf of the National Sheep Association, chiefe executive Phil Stocker strongly disagreed with the programme's claims: “You don’t get rams that are gay," he insisted. "You find rams with high sex drive that will ride anything but they won’t have full sex with other rams. It’s a nonsense.

"In my experience you get females riding each other and you’ll get males riding each other but they’ll never perform a full sexual act and it’s never in preference to a female. It’s born out of high testosterone levels. They can smell ewes that are fertile and they’ll ride anything available to them," he said.

“The only reason farmers would cull rams is because they’re infertile and are firing blanks. Some will have low testosterone and have no interest in working at all but this is incredibly rare.”