The Monforts of Colorado have been riding the crest of the nation's cattle wave for more than 45 years. The Monfort empire long predated the other large-scale commercial operations that boomed in the Southwest in the 1960s.

Warren H. Monfort began fattening a few animals on his 80 acre farm in Greeley, Colo., in 1930. By 1945, he was ftwo huge Monfort fattening yards at Kuner and Gilcrest now handle 450,000 heads a year and the modern Monfort packing plant slaughters at least that many.

Kenneth W. Monfort, Warren's son, presides over an empire with annual sales of $300 million. But he still seems more like a cattleman than a businessman. His employees - he has 2,000 of them - call him "Kenny," as do the ranchers at a cattlemen's cafe in Greeley where Monfort sometimes goes for soup and crackers at lunchtime.

Monfort seems resolutely determined to keep it that way. He had the engine of his old car rebuilt rather than buy a new one, and he quibbles with his wife (who cooks the family dinner herself) about whether to buy a new rug for the home. Monfort, a Democrat, served in th Colorado legislature in the 1960s and he talks about running for something or doing some ranching someday. But for the moment, Monfort of Colorado, Inc., is in the thick of the changes sweeping through the beef economy, and Kenneth Monfort has his hands full with business.