THE INTERNET has become an important tool for cattle breeders. Just ask Carlos Guerra, who has 400 cattle on the 6000 acres he ranches in Linn, Texas. Guerra, a fourth-generation rancher, has used the Internet to market his cattle for four years.

"It was a much slower process before that," says Guerra. If a prospective buyer wasn't local, Guerra would have to take photos, get them developed and send them to the buyer. With numerous phone calls back and forth, at least two weeks would transpire before a sale was made. Today, using the Internet and e-mail, a sale can be completed in a matter of hours.

Rex Ruckert of Internet Access Corp. is even more enthusiastic about the new technology, going so far as to comparing its importance to the invention of the printing press.

"The Internet has revolutionized commerce," says Ruckert. A cattle breeder with a web site has a definite advantage over the one who is still doing business the old-fashioned way.

Guerra sells to many out-of-state buyers, but his first Internet sale came as a surprise. "He thought he beat all the bushes in south Texas," says Ruckert. "Then when a prospective customer saw Guerra's Web site, La Muneca.com, and purchased a Simbrah heifer from him, it turned out the buyer lived only a few miles down the road in Edinburg."

The marketing of bull semen on the Internet is even more significant to the cattle industry than the sale of cattle. Ruckert also owns the web site Semenclub.com where an interested party will find color photos of bulls whose semen is indexed by breed, pedigree and other data.

This web site can also be used to perform a search by the bull's name and registration number, or to find other bulls sired by a certain one. It is also possible to invest in a specific animal by buying a percentage of all future semen production from him.

Guerra's La Muneca web site can be accessed from Semenclub.com. At the click of a mouse, photos and data on Guerra's champion stock are available for people all over the world to look over.

Guerra, whose family has been in the cattle breeding business in south Texas since the late 1800s, is proud of his 400 registered head of Simbrahs and Red Brahmans.

He is especially proud of an award winning Red Brahman whose head is mounted on the wall in Guerra's office. There is reason to be proud since this one bull's semen has been sold for over half a million dollars.

Guerra maintains that there is no better insurance on a good bull than to have a bank of his semen stored. "You can sell the bull at a marketable age and still retain his semen for future use."

Semen can be extracted from the animal by an electronic ejaculator, which is done in a laboratory setting. The fluid is put under a microscope, labeled and mixed with materials that allow it to be frozen. Another method, considered superior, is to allow the bull to copulate, diverting the semen at the time of penetration.

Semen is put into units called "straws." A "cane" holds 10 straws, which has the potential of breeding ten cows. The average cost of a straw is $40 but can go for more or less depending on several factors, such as the quality of the bull's progeny.

Units are stored and shipped in containers of liquid nitrogen that keep the contents at a temperature of minus 320 degrees. The semen can be kept indefinitely in the liquid nitrogen, which usually needs replenishing in 60 to 90 days.

The semen from Guerra's bulls has been sold all over the world, made possible by the Internet