The event was witnessed by more than 7,000 farm laborers who converged at a United Farm Workers compound here to celebrate an outdoor Mass of thanksgiving held beneath an immense white tent festooned with UFW flags and posters.

Ethel Kennedy, the widow of Robert F. Kennedy, and her children, Kerry, 27, Christopher, 25, and Rory, 20, received a standing ovation when they entered the tent with clenched fists held high.

Chavez went on the fast July 17 to seek an end to the use of pesticides that he said endanger farm workers, consumers and the environment. He also sought support for the UFW’s four-year boycott of California table grapes and its efforts to win labor contracts with growers.

Mother and Wife With Him

During the Mass, Chavez shared communion with his 96-year-old mother, Juana Chavez, and his wife, Helen, who fanned her husband with a manila folder and provided him with sips of water from a plastic tumbler.

At one point, Chavez handed a small cross fashioned from twigs to former presidential candidate Jesse Jackson. The tendering of the cross symbolized the start of Jackson’s own three-day fast to “share the burden.”

“Today, I pass on the fast for life to hundreds of concerned men and women throughout North America and the world who have offered to share the suffering,” Chavez said in a statement read to the mostly Latino audience by his son Fernando, 39. “They will help carry the burden by continuing the fast in front of their local supermarkets.

“The fast will go in hundreds of distant places,” Chavez added, “and it will multiply among thousands and then millions of caring people until every poisoned grape is off the supermarket shelves.”

Throughout the Mass, Chavez squinted in pain and clutched his stomach. He wiped his brow with a white handkerchief as he sat in a rocking chair placed before an altar decorated with bouquets of flowers.

“This is a tremendous relief for us,” Fernando Chavez said in an interview.

“This morning he was very, very sick and suffering from dehydration.”

He added: “But my mother is the unsung hero of the day. For the past four days she has been at my father’s side 24 hours a day, somehow taking it all in stride.”

After the Mass Chavez was taken by car to an undisclosed location where he was to receive light miso broth, a special rice mixture, to restore his health. Chavez has refused to take any medication.

Chavez, who has already lost more than 33 1/2 pounds of his original weight of 174 pounds, suffered from intense stomach cramps, dehydration and nausea, according to his physician, Marian Moses.

“We expect that it will be at least a week to 10 days before he is on solid food,” Moses said, “and a much longer time before he is back to his state of health before he began the fast.”

By not eating for 36 days, Chavez eclipsed his 25-day fast in 1968 for UFW members to maintain their commitment to the principles of nonviolence. That fast ended when Chavez shared bread with Sen. Robert F. Kennedy.

Grapes ‘Washed With Tears’

“The day is coming soon when grapes will no longer be washed with the tears, sweat and blood of workers in the field,” said Kerry Kennedy. “No compre uvas (Don’t buy grapes).”

Later, Jackson, along with actors including Martin Sheen and Robert Blake, received rousing applause when they invited others to join them by fasting for three days.

“I get grumpy when I miss breakfast,” Blake said in an interview. “But I’m going to do it.”

Chavez, an ardent admirer of Mohandas K. Gandhi, who often fasted to protest conditions in India under British rule, called his fast a “fervent prayer that, together, we will confront and resist the scourge of poisons that threatens our people, and our land and our food.”

UFW officials have attributed an unusually high number of birth defects and cancer deaths among children in the nearby community of McFarland to the use of pesticides.

State and federal health investigators studying the problem, however, have been unable to determine the cause of the cancers.

Meanwhile, growers, store owners and state health officials insist that pesticides are strictly regulated and pose no cause for concern. Beyond that, they argue that the same pesticides are used on a variety of commonly eaten fruits and vegetables that have not been targeted by the boycott.

Still, UFW leaders said Chavez’s fast has achieved its main goals of prompting public protests against the sale of table grapes and boosting support for the union.

‘Public Awakening’

“I am personally grateful that Cesar came through this safely,” said Dolores Huerta, vice president of the UFW. “The public awakening he wanted has happened.”

In the last month, Mayfair, Safeway, Lucky, Save Mart, Ralphs, A&P; and Vons markets throughout the state have been picketed by union members and concerned citizens. In addition, a spokeswoman for the Mexican-American Grocers Assn. said 30 of the 900 stores her group represents in California have stopped selling grapes.

Whether these activities, which Huerta has called a return to our “tried and true weapons,” will significantly impact sales of grapes remains to be seen.

Judy Decker, a spokeswoman for Lucky markets, acknowledged that there has been a “local effect” on grape sales at stores that have been picketed.

But Cassandra Pye, a spokeswoman for the California Grocers Assn., which represents 7,000 stores in California, said the overall impact has been negligible.

“Consumers have not definitively responded one way or another to this thing,” Pye said. “Supermarkets are living through these demonstrations.”

Bruce Obbink, president of the California Table Grape Commission, was more blunt.

“I think it is a tragic expense of human energy and time because there is no way it will translate to the needs of farm workers,” Obbink said. “Those farm workers who want to belong to a union need elections, they don’t need boycotts or fasts.”

No Pacts With Growers

The UFW has no contracts with table grape growers and only 80 contracts throughout the country. The union’s power has eroded dramatically since George Deukmejian was elected governor in 1982.

In 1975, the state Legislature enacted the Agricultural Labor Relations Act, which gave farm workers a formal means of settling grievances and the right to secret-ballot elections to decide which, if any, union should represent them.

Deukmejian, believing that the board’s actions favored farm workers, cut the agency’s budget and appointed a conservative Republican as its general counsel. Prosecution of unfair labor practice charges diminished substantially and Chavez accused the board of no longer securing workers’ rights.

“The law is not serving him the way he wants it to serve him,” Obbink said. “The union’s real issue is not pesticides. The real issue is contracts.”

Catarina Ruiz, 30, of nearby Hollister, disagreed. “The fact is people are being poisoned by pesticides and there are many sick babies in this area,” she said in Spanish. “When Cesar acts, things change.”