After an emotional four-hour hearing, San Mateo County supervisors have tentatively approved a six-month ban on dog and cat breeding aimed at reducing the county's overpopulation of unclaimed pets.

The proposal, the first of its kind in the nation, will get a second reading Dec. 11, when a licensing procedure for breeders will be discussed, said Supervisor Tom Nolan, who introduced the legislation.Unless zero growth in the pet population can be shown after six months, there will be mandatory neutering and spaying in the unincorporated areas of the county, according to the ordinance. Violators face fines ranging from $100 to $500.

Kim Sturla, Peninsula Humane Society executive director, said her organization annually is forced to kill 10,000 unclaimed animals.

Before this week's Board of Supervisors meeting, the plan called for a one-year moratorium. That was reduced to six months.

The county also agreed to put up $15,000 for free spaying and neutering clinics in unincorporated areas.

Said Nolan, "By the December date, plans will be drawn up to name an advisory committee, of either nine or 11 members, representing such groups as breeders, veterinarians, the Humane Society and kennel club members to consider other possible changes."

The ban is effective on Jan. 1.

"I think we made some real history today - to right a long-enduring wrong. I am really proud of it," said the supervisor, who said the issue had triggered more correspondence and phone calls to his office then any issue during his six years in office.

An estimated 250 people crowded into a room Tuesday to hear and give testimony, much of which focused on the mandatory spaying and neutering proposal.