The Loudoun County Board of Supervisors Monday rejected 5 to 3 a proposal to fund a new position for an agricultural development officer to help promote the county's main industry, agriculture.

Instead, the board sent the proposal to its Policy Committee and charged it with finding a private group that could pay for the position. The new position was proposed in July by board Chairman Frank Raflo after a meeting attended by nearly 100 persons, most of them farmers.

As outlined in a report by the Agricultural Advisory Committee, an agricultural development officer's duties would include promoting the farming industry, educating the public on the role and benefits of farming in Loudoun and developing high value crops and new marketing outlets. The gross value of farm products in Loudoun in 1982 was $29,022,000. About two-thirds of the county's land is in farming.

Blue Ridge Supervisor James Brownell, a farmer, made the motion to create a county-funded position at a cost of about $30,000. The temporary position was to be for one year to determine its importance to the county.

But the board acted on a motion by Dulles Supervisor Anne Kavanagh to refer the matter to the policy committee, which will look for an organization that would be willing to create and partially fund such a position, with the county funding about half.

"I can't think of one farmer's group that would be willing do this," Brownell said, "although the Chamber of Commerce might be interested."

Farmers in Loudoun, he said, are "hanging on by a thread. I think this would help them."

An angry Raflo said after the meeting that the eastern supervisors who promote industrial development "shot themselves in the foot" by coming out against the agricultural position. He cited a report by John Naisbitt, author of "Megatrends," which said business is most interested in the quality of life when deciding where to locate. Loudoun County was listed as a desirable area because of its vast agricultural lands, the report said.

Supervisor Andrew Bird III, who was vehemently opposed to the new position, said he is against the county paying a lobbyist for any one industry. "This $30,000 seed will become a $300,000 weed," he said. "I am against this position in any form."

Kavanagh agreed that as Loudoun's main industry, farming is important to the whole county, and that some taxpayers' money should be used to fund the position. "I would just like to look at another mechanism for running the office rather than having the county do it," she said.

In other action, the board unanimously approved a motion to amend the rabies ordinance to allow domesticated ferrets and other animals "not indigenous to the county" to be destroyed if they have the potential of exposing a human to rabies. The amendment also would allow the owner of such an animal to offer sworn proof that the animal has never been out of the house or otherwise exposed to rabies.

Environmental Health Director Earl Virts said his office requested the amendment because more people in the county are acquiring ferrets as pets and nothing is known about the incubation period of rabies in ferrets. Two persons have been bitten by ferrets in the last six weeks, Virts said. The ferrets were destroyed.