The broader-umbrella approach is working. Take the case of Wolfgang Puck. In March, he announced that he would stop serving foie gras and buy eggs only from chickens not confined to small cages. Veal, pork and poultry suppliers will have to abide by stricter standards, too.

For five years before the announcement, Mr. Baur’s group had been pressuring Mr. Puck to change his meaty ways. Mr. Puck, in an interview in March, said that had nothing to do with his new policies. He simply came to the conclusion that better standards were the best thing for his customers, his food and the animals. But he did credit the Humane Society for his education.

Mr. Puck met Mr. Pacelle through Sharon Patrick, a branding consultant he had hired. Ms. Patrick, the former president of Martha Stewart Living Omnimedia, believed animal welfare could be an important component in her plan for Mr. Puck.

She brokered a meeting between the two men, and eight months later Mr. Puck presented his new animal welfare plan.

But farmers and corporations are only gingerly endorsing animal rights groups — if at all.

The flurry of corporate animal welfare policies that began in 1999 with McDonald’s are simply sound corporate strategy, company representatives say. The genesis was likely the 1993 E. coli outbreak at Jack in the Box restaurants, which sickened hundreds and killed four children. Companies realized they had to get a better handle on where their meat was coming from.

And they say it had nothing to do with PETA.

“Ask them and they will tell you they are the sole responsible party for bringing all these changes, but I have yet to see one of their campaigns produce results where they affected the company in terms of customer traffic or profitability,” said Denny Lynch, a spokesman for Wendy’s.

Like other big fast food companies, Wendy’s has been a target of animal activists’ campaigns. Earlier this month, it announced a strengthened animal welfare policy.