THIS WAS WHAT I'D BEEN WAITING :for:my first shot as a film critic. Okay, so they weren't exactly sending me to a world premiere with screaming crowds, dark-windowed limos and starlets overflowing their evening gowns. I could deal with that.

Go to the Rayburn House Office Building, they said. What? To the World's Ugliest Building to review a movie? Be there at 5 p.m., they said, to see "The Story of Modern Beef," produced by the National Cattlemen's Association. Boy, did I get the wrong movie. I'm a vegetarian.

Well, Siskel and Ebert started at the bottom, right? Besides, I figured, a lot of talented young filmmakers cut their teeth doing documentaries. I'll probably see scenes of trail-weary cowboys driving longhorns across the wind-whipped panhandle toward Dodge City, then dissolve to the "city of the broad shoulders," Chicago, with teeming stockyards and the flash of slaughterhouse knives. I hail a cab, hoping "The Story of Modern Beef" is going to be a cine'ma ve'rite' sleeper, boeuf noir.

The reception is crowded with National Cattlemen who look remarkably like paunchy businessmen wearing pointy-toed cowboy boots. None of them looks trail-weary, though a few have worn vinyl pocket protectors. Everyone is talking at once, some in Texas twangs that could cut glass, and the place throbs like Saturday night at Miss Kitty's Longbranch.

Long tables filled with serving trays dominate the room's center. Above the main table stands a three-foot- long, 18-inch-high steer artfully carved of cloudy ice. The heroic animal looms above the Beef Thai Ribbons, its crystal-clear horns pointing straight ahead. But I'm surprised to see the steer's tail distinctively arched above its rump. That's the cow equivalent of a dog raising its hind leg, which is not

what you expect with your hors d'oeuvres.

The room is darkened, the film is projected and my career as arbiter of the cinema ends in the same moment. This isn't a film at all, but a 10-minute industrial-strength videotape filled with bland, talking heads. A supermarket manager, nutritionist, physician and feed-lot operator tell us it's a "trendy thing to eat red meat," and they rattle off statistics about saturated fat and blood cholesterol and the joys of eating lean, young, muscular cattle. Every other shot shows disembodied hands slicing beef into thin, surgically trimmed slices.

I pack up and head out to a rain-swept Independence Avenue. I reckon that's "The Story of Modern Beef," pardner. It's squeaky clean, plastic wrapped, low fat, rich in essential nutrients and flat-out trendy. No cattle drives, no cowboys, no sweeping desert vistas, nothing to remind you of Howard Hawks or John Wayne. But it is classic tragedy: The cow dies at the end.