The National Chicken Council urged Congress yesterday not to tinker with the laws governing the relationships between growers and the integrated companies whose chickens they produce under contract. "Today's and tomorrow's market forces compel U.S. agribusiness to work across the links in the food chain to grow the opportunities for all," said NCC Senior Vice President William P. Roenigk in testimony to the Subcommittee on Agriculture, Rural Development and Related Agencies of the Senate Appropriations Committee.  "It is not a time to legislate and regulate about how best to arrange the links in the food chain."