John A. Hamann, 75, a poultry expert at the Department of Agriculture who retired in 1974 with 35 years of service, died Dec. 18 at Prince George's General Hospital in Cheverly. He had a heart ailment.

Mr. Hamann, who was born in New York City, was graduated from the University of California at Berkeley and later worked for the Poultry Producers of Central California. He began his career with the Department of Agriculture in California and subsequently worked for the department in Missouri and Texas.

In 1952, he was transferred to Washington, where he engaged in research on poultry and worked on poultry marketing techniques. At the time of his retirement, he was chief of the Dairy and Poultry Products Marketing Laboratory at the Beltsville Agricultural Research Station.

Mr. Hamann received a Certificate of Merit and two Superior Service Awards from Agriculture. He helped draft an egg law for Alaska and presented papers at World Poultry Congresses in Australia, the Soviet Union, Spain, Germany and Sweden.

A resident of Cheverly, he was a member of the Redeemer Lutheran Church in Hyattsville and the Civitans International.

Survivors include his wife, Elfriede, of Cheverly; a daughter, Joan McIntire of Gambrills, Md., and son, John, of Bladensburg; a sister, Claire Meeson of Summit, N.J.; two brothers, Carl, of Ticonderoga, N.Y., and Frederick, of New York City, and six grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the John A. Hamann Memorial Fund, Redeemer Lutheran Church, 3799 East-West Highway, Hyattsville, Md.