The "kill floor" on a modern beef slaughtering plant is far removed from the wretched, unsanitary conditions described in Upton Sinclairs muckraking novel about the Chicago meat industry, "The Jungle."

At Monfort of Colorado, Inc.'s high-speed plant here, steers weighing half a ton are killed and cut into pieces at the rate of five a minute. It is a model of American efficency, but the noise, the nauseating odor, the steamy air and the blood running across the floor still testifies to the grisly nature of the work. A skull-penetrating pneumatic bolt exerting 1,800 pounds of pressure per square inch instantly kills the animals behind a screened area where they enter the facility. Seconds later, they are cut open and hoisted, head down, onto a moving overhead cable.

As their bodies edge along the overhead cablen large metal clamps reach around to attach onto the hide at an incision along the stomach. The bodies jerk violentlh as the devices pel off the skins and drop them down a hol. At one end of the kill floor, severed cattle heads, attached to hooks, bob past meat cutters who trim off the flesh.

A moving "viscera belt" carries the animals' stomachs, intestines, livera and other organs past sorters dressed in white uniforms. These specialists pick out the livers and drop them down a chute to other workers on a lower floor. Within minutes of that, the livers are washed, neatly boxed and on their way to a freezer.

Meanwhile, men in rubber boots constantly spray the floor and the belts to flush away blood and debrism.

It is truism in the packing business that "everything is used except the bellow." Beef animals provide some 10 able by-products besides meat. Collecting "drop," more than offsets the $26 that Monfort figures it costs in labor and other expense to kill each animal.

A 1,000-pound steer yields only an average 432 pounds of red meat. Nearby all the rest is used, though, in products ranging from medicines to cosmetics and clothing. Spleens, lungs, inedible livers and kidneys are processed as fish and pet food. Parts of leg bones are made into gelatin for film processing. Blood is caught in stainless steel tanks and sold to processors who dehydrate it for use in shoe polish or as a plywood bonding material. Beef pancreas glands are used to make insulin.

Hearts, head meat and stomach tissues are made into sausage meat, and brains, kidneys, oxtails and tongues are exported, mainly to England and France.

Fat, hooves, bones, intestines and stomachs are sped by conveyor belt to two large rendering plants which cook the material at high temperature to make edible tallow (used in shortening and certain cosmetics, such as lipstick) and inedible tallow (for soap and animal feed).

The cattle by-products also serve other manufacturing uses: glue, buttons, toothbrush handles, gelatin, coating for pills glycerin for explosives and curled hair for upholstery.

But the most valuable product of the beef animal is still its meat. Monfort and other modern packing operations attempt to get the maximum value from it by doing almost all the cutting in the plant.

After chilling for 48 hours, the carcasses are put on the overhead disassembly line again. Butchers using power saws make the first big cuts as the carcasses swing by. Then men and women with knives carve up these veyor belts. The resulting loins, sirloins, ribs chucks and rounds are vacuum packed in plastic bags and placed in cartons that can be shipped anywhere in the country.

One floor below are the hamburger manufacturing operations, with a capacity to turn out more than 1 million a day. Machines press the ground meat into perfect round and oval hamburgers ready for the grills of the nation's fast-food restaurants.