Something's afoot in the conservative world of dog food. For decades, the advertising approach has been the same: buxom ladies in tartan skirts and sensible shoes extolling the virtues of their chosen brand. "Dog food X is top-hole for Flash's coat or Lucky's teeth," they say. You can only agree. Why? Because top breeders (and they really are, not actors) recommend it.

In recent years, admittedly, the style has softened. Fearsome, Barbara Woodhouse types have been replaced by a younger brigade who, on occasion, even let their dogs run free. Cue lingering, slow-motion shots as assorted pooches charge across rolling hillsides, muscles rippling and ears flapping. (Only cats like Arthur, it seems, have a sense of irony in their advertising.)

But wait. What's Pedigree Chum up to? Its new TV campaign for Chum Complete features grainy scenes of exploding shells, firing guns and running men.

We're in the trenches of a First World War battlefield where, we learn, a special breed of dog called a briard was used by the medical corps to hunt out wounded men. Never too far away, a husband-and-wife dog-breeding team explain to the uninitiated that these canine heroes' coats served to protect them in the battlefield. "These days, the job is done from the inside with Pedigree Chum," is their somewhat laboured link to the present day.

The ad is part of a gradual attempt by Pedigree to jazz up Chum's long- running "Top breeders recommend it" campaign, explains David Watson, a company spokesman. The last commercial focused on Eve, and her productive bitch Kashmir. ("Super food for a super-mum," we were told). In the new ad, top breeders still recommend it, but now there's an added twist to add "personality" and "humour", says Watson. "The idea was to continue our campaign theme, but make the different breeds of dog become more of a hero."

Apparently, recent research revealed scepticism amongst certain portions of the dog-owning public as to whether breeders really love their dogs as much as everyone else. The ad was designed to show that, yes, they really do, and to add another level of expertise to the advertising message by adding the story of a particular breed. (Sceptics may be forgiven for thinking there could be another reason: that reliance on members of the public rather than actors results in dull, formulaic ads.)

The First World War reference may be an oblique way to grab the viewer's attention, but it does reinforce Pedigree's positioning as the brand that understands dogs, owners and the relationship between the two. Which is why the brand continues to rely on its "Top breeders ..." tag line. In this business, endorsement is everything.

"Other experts watching the ad will recognise and respect their view. The dog-owning public then gets the message from opinion formers," Watson continues. It works just like publication of a scientific paper, you see. The endorsement must be reviewed by the experts' peers first, before it is presented to the rest of the world, he adds. And you thought they were just advertising dog food.

Meg Carter