When does a farm become a business?

How the court case settles the dispute between the 23.4-acre farm and its neighbors is expected to be studied closely by many other Massachusetts farmers who are worried about the future of their livelihood.

“This challenges one of the things that makes agriculture viable in Massachusetts,’’ said Douglas P. Gillespie, executive director of the Massachusetts Farm Bureau Federation. “We’re in a state that has high land costs and high labor costs. We’ve always had to do something - retailing or value-added agriculture - to make it work.’’

For now, there’s no quarrel with Sweet Meadow’s retail outlet; it’s the mixing of its own brand of pet food that led to the legal battle.

On one side are Sweet Meadow’s owners, John A. and Katherine Knapp, their daughter Patty Michaud, and her husband, Albert Michaud. In addition to their annual hay harvest, the Knapps and Michauds have a petting zoo, a riding stable, a produce stand, and their own brand of chicken, guinea pig, and rabbit food. All of it permissible, they say, under local and state agricultural laws.

On the other side are neighbors of the Coolidge Street operation who contend that its pet-food business has brought a steady stream of trucks, noise, and acrimony to their once-peaceful roadway. Most importantly, they assert, it violates the zoning laws.

“I think the riding stable is great, and it makes sense,’’ said June Ouellette, one of 18 neighbors who have petitioned various town boards to more closely monitor and regulate Sweet Meadow’s operations. “But I don’t know how anyone could look at Sweet Meadow’s pet-food business and say it’s a farm. It’s not. It’s a business.’’

In September, the town’s Zoning Board of Appeals issued a cease and desist order that, for now, gives Ouellette and her neighbors the upper hand. The ruling prohibits Sweet Meadow from bringing in the ingredients for its pet food.

The decision was immediately appealed in Middlesex Superior Court by the Knapps and Michauds, who are now waiting for a court date.

Without the imported ingredients - dried fruit, yogurt bits, hay, herbs - they say Sweet Meadow Farm would be hard pressed to continue making its profitable line of pet-food products.

“The pet food is 80 percent of our business,’’ Albert Michaud said. “Without it, well, we would really have a hard time getting by.’’

Getting by is an overriding issue for most of the state’s farmers, said Stephen Verrill, co-owner of Concord’s Verrill Farm.

“The days are over when you could make a living selling one or two items on the wholesale market,’’ he said. “You have to have enough of a mix.’’

With so much at stake, the Michauds are hesitant to discuss the particulars of their appeal, but they are passionate about their vision for Sweet Meadow. Patty Michaud points to the stables, where she conducts horse-riding and animal-training classes.

“We’ve given to the MSPCA and we’ve been very involved in animal rescue, which is something no one ever talks about,’’ she said of the farm’s critics. “We have been giving back.’’

Over the years, neighbors have brought numerous complaints to town officials, particularly Sherborn’s Conservation Commission. Almost all of the complaints have been dismissed, said the commission’s chairman, Steve Gaskin.

“We’re always happy to look into things, and we have always tried to keep an eye on this property, to objectively administer the law,’’ Gaskin said. “But generally we find that something that would be a violation’’ for a residential property “is allowed because they are a farm.’’

The zoning board’s chairman, Michael Giaimo, said his panel’s Sept. 21 order was not intended to put a financial squeeze the farm, one of four remaining in this once-booming agricultural community.

“This town has a strong farming heritage, and we respect that,’’ he said.

Giaimo said that state and local agricultural laws allow farms to import material, such as feed, for consumption on the property, and also allow farms to export items, such as produce, grown on the premises. But they don’t allow farms to import materials for the sole purpose of repackaging and exporting them for sale.

“To the extent that they grow hay on their farm, they could continue using it to make their pet food. This order does not stop them,’’ he said. “And there are other aspects of the farm - its petting zoo, riding stables, and farm stand - that are completely unaffected by our ruling.’’

His board’s ruling does not go far enough, according to Jennifer Hawkins, the Coolidge Street neighbor who initiated the complaint. Hawkins said she plans to appeal the zoning board’s decision because it allows Sweet Meadow to continue selling products, like pumpkins, not grown on the farm.

Hawkins is also involved in a separate court battle with the Knapps over a 40-foot strip of land that runs by her home. She said that dispute - wending its way through Middlesex Superior Court - has nothing to do with her fight to stop the pet-food operation.

“This business should not be operating in a residential district,’’ she said. “People shouldn’t use agriculture to cover up manufacturing or industry.’’

Farm bureau executive Gillespie said the Sweet Meadow case raises troubling questions for more than 7,000 working farms in the state.

“To the extent that Sweet Meadow has brought in items to add value to their own products - in this case, hay - we have to ask ourselves whether it’s any different from an apple farm that makes and sells apple pies,’’ he said. “Do we require them to grow the flour, too?’’

Gillespie said that in a typical year, Massachusetts farmers will be involved in 20 to 30 zoning disputes.

“This one’s a little different,’’ he said, “because they are challenging value-added products. There is no number, no percentage that applies here. . . How much flour do you need to make a pie?’’