They agree "it's a lot of bull." But whose bull is it?

Georgia millionaire John B. Amos claims two-thirds of Franchester of Wye, a $100,000 Angus bull, belongs to him. Daniel Minchew, a former aide to Sen. Herman E. Talmadge (D-Ga.), says the bull is his.

The two have locked horns in circuit court in rural Berryville, Va., 45 miles west of Washington, asking a state judge to decide who gets Franchester.

Amos, the head of a leading cancer insurance firm, claims he gave Minchew, Talmadge's chief accuser in recent Senate Ethics Committee hearings, the authority to purchase the prize Angus for him for $150,000. But unknown to Amos, the Georgia executive now claims, Minchew already had bought an interest in the bull himself at a public auction several days earlier for $100,000.

A one-third interest in the bull still belongs to Wye Plantation, the Maryland farm that sold Franchester to Minchew at auction on May 8, 1978.

A spokesman for Minchew yesterday denied that Minchew had been asked to buy the bull for Amos. The spokesman said instead that Minchew had asked Amos to get a loan to purchase the animal.

While the attorneys argue the fine points of agency and contract law, Franchester spends his days in a veritable "bull heaven," according to one of his keepers, Charles Anderson Jr. of North American Breeders Inc. Farms of Berryville.

The bull is being kept at the stud farm until the court decides his future.

Franchester, said to be one of the country's finest Angus bulls, wanders over his own lush half-acre lot, complete with a small house offering shade, feed and a cool drink.

At nearly 6 feet and 2,400 pounds, Franchester is a quiet, coal-black bull whose sees is pure gold. Each unit, or ampule, or his sement sells for $10, according to Anderson. For another $20o, the purchaser can get a certificate documenting the semen is that of Franchester, a pure-bred Aberdeen Angus.

His semen already has been sold to breeders from Canada to Brazil, from California to South Africa, Anderson said.