When you think about it, a sheepdog has the best job in the world - one that every dog would wish for. He gets to run after lots of sheep - legitimately. Tomorrow, the four-day Enfer World Sheepdog Trials begin at the Charleville estate in Tullamore, Co Offaly. Rosita Boland reports

It's the first time the World Trials will have been held in Ireland and the organisers are not sure how big a crowd will turn up . Loughlin Hooper, who is working with the event, reports that the organisers have been expecting between 15,000 and 20,000 visitors in total, but that the Garda Síochána has told them to expect a crowd of anything up to 30,000 on Sunday alone, the last day. However, a few figures are certain. There will be 240 top-class dogs there, accompanied by 190 handlers from 21 countries. Each handler is allowed a maximum of two dogs.

B&B proprietors around Tullamore have been getting some unusual phonecalls from overseas. They're concerned not with their own sleeping arrangements, but those of their dogs. They have been asking if it is possible to keep their dogs indoors, and some have even requested that the canines share the human sleeping accommodation. It's not only the fear of theft that is prompting these requests. A lot of the dogs are from countries such as Norway, Switzerland, Finland and Canada, where the temperatures drop far below freezing, and they are used to sleeping either indoors or in heated kennels. With a world champion title at stake, some handlers are not prepared to risk exposing their sheepdogs to the unpredictable phenomena known as the Irish summer.

Con McGarry, who has a sheep farm at Ballyglass, near Castlerea in Co Roscommon, is the current Irish National Sheepdog Trial Champion. In 2000, McGarry also took the One Man and His Dog title. You'd know dogs are important on this farm once you see the pillars at the entrance to the farmhouse. No grandiose lions or eagles for these pillars; there's a sheepdog either side. McGarry's other half is Dan, a four-year-old pure-bred border collie, who starts barking with wild joy the instant he hears McGarry approaching his kennel. Dan isn't the only dog barking at Ballyglass: McGarry breeds and trains sheepdogs, so there are a score or more dogs in the yard, ranging from puppies a couple of months old, to nine-year-old Gyp.

"The working life of a dog on a farm is about 11 years," says McGarry. "A good dog could handle up to 200 ewes and lambs, perhaps more if circumstances weren't too difficult. If the terrain was hillside, with rocks and gullies where the sheep could run off into, then you'd need more than one dog."

McGarry is anxious to point out that there is a gulf of difference between show dogs and trial dogs. Show dogs are dogs with no jobs. They only have to look good and highly groomed. Whereas a trial dog - they're the dogs with the jobs. "To be a good trial dog, the dog must be able to do farm work confidently. It's like a county footballer or hurler, when you put them at club level, they need to be exceptionally good."

He unfastens the door of Dan's kennel and a lean streak of dog flies out. Dan is a dog who is all energy; pointed ears and legs like pistons. He accepts a pat with dignity, but it's the sheep and the fields beyond the kennels that he's really interested in. He races off towards the field, waiting for instructions.

So is the sheepdog still an essential part of a working farm, despite all the recent mechanisation? "It's even more essential," stresses McGarry. "With the high exodus of people leaving the land, most farmers have less and less help now. It's often just the farmer and his dog. A farmer can go out alone with his dogs and get the sheep or cattle in. Without a dog, he couldn't do that. Quad bikes are very effective when the stock don't know them, but once they get used to them, they're useless, and they only work on level ground anyway."

So what makes a champion dog? "Breeding, brains, and the ability to listen to his master. You only really know how they are going to be after six months' training. Some dogs might be a bit nervous and scatty: they'll be good farm dogs, but they won't make trial dogs. A trial dog needs to be very good at running out behind a stock, approaching them quietly and taking them steadily to the handler. You can sell them on, too; a good dog will work with any handler."

We're out in a field, and there are several sheep grazing at the other end. Dan looks at them with a fixed eye. He knows that McGarry will be giving him instructions, and he can't wait to be off. He's quivering, like a taut spring. He glances from the sheep to McGarry. He's on a "stand and look" command, which is a signal to get ready. McGarry shows me his whistle. It's like a small half-moon disc, with a hole in the middle, which he puts in his mouth. He will direct Dan by a series of calls and whistles. A dog can hear the whistle up to a mile away.

Once Dan gets the "off" signal, he's gone. He keeps close to the ground as he runs, almost like a stalking cat, or a greyhound. His tail is firmly between his legs, so he's all aerodynamic, pure movement. For the next 20 minutes or so, I watch the assured, lovely unity between dog and handler. Dan rounds up the sheep, takes three of them off, then rounds them up right in front of me. He responds instantly to each of McGarry's commands: go left, go right, lie down. He's far enough away from the sheep each time for them to be utterly calm at his rounding up. They trot around the field in an orderly manner.

At Tullamore, there are 800 sheep all lined up for the dogs to work with over the four days of the trial. Tullamore is a lowland green course, but there are some trials that are mountain courses, with rougher terrain.

At one point in the workout, Dan stands by a gate at the far end of the field, listens to the next command, and then he's gone. He has dived in through the barred gate and is racing off across the yonder fields. He is out of sight in a matter of seconds. "That command was to 'look back'," says McGarry. He's gone back 500, 600 meters, for sheep he cannot see, but he will find them and bring them back."

We go up to the gate to watch. Once or twice McGarry blows on the whistle again. "What does that sound mean?"

"It means, 'come on!'," McGarry grins. At the trial, dog and handler have 15 minutes to complete their course. If they haven't done it by the time the bell goes, they lose points. At the final, they will have 30 minutes to work together.

On the horizon, like a white sea, scores and scores of sheep appear, trotting tranquilly towards us, Dan running round them in wide arcs, keeping them perfectly together. "That'll do," McGarry calls, and Dan flies back through the gate again. He must be tired, after all that running, but he's watching the sheep in our field again, ready for more action. "That'll do," McGarry repeats. Dan virtually backs out of the field, still watching the sheep; a dog who clearly loves his job, and who seems determined to give the 239 other dogs a run for the title of World Sheepdog Champion.