NORTHBROOK, Ill. (AP) _ Imcera Group Inc., a maker of health care products and chemicals, said today it will cut 1,000 jobs worldwide in a previously announced restructuring of its Pitman-Moore animal health care business.

The company said it will close 11 of its 27 plants in the United States, South America, the United Kingdom and Pacific Rim nations. About half the jobs being eliminated will be cut immediately and the rest over the next two years, the company said.

The job cuts represent about 30 percent of the division's work force of 3,200. The parent company employs about 9,500 people worldwide.

Pitman-Moore also will halt development of a drug designed to produce leaner pork, Imcera said in a news release. The porcine somatotropin product, with the brandname Grolene, had been under development at a new plant in Terre Haute, Ind.

Imcera, which is based in the Chicago suburb of Northbrook, said it was exploring various options for the disposition of the Grolene plant.

Imcera, which earned $127.5 million in fiscal 1992, announced in March it would restructure Pitman-Moore to improve future earnings prospects. The unit has been hurt by competitive price-cutting in the feed-ingredients sector and delays in reopening a Kansas City, Kan., veterinary products plant that was closed last year to bring manufacturing processes up to federal standards.

Grolene's potential has been reduced by a protracted Food and Drug Administration approval process, a shrinking market due to improved genetic methods of producing leaner pork, expected consumer resistance to the product and numerous competitive products in development, William J. Mercer, president and chief executive of the Pitman-Moore unit, said in a statement.