Drugmaker Eli Lilly and Co.'s Elanco animal health division plans to buy a privately held maker of feed-enzyme products that improve poultry, egg and meat production.

Terms of the acquisition of ChemGen Corp. were not disclosed. Lilly said Tuesday the deal is expected to close in the first quarter.

Lilly, headquartered in Indianapolis, said feed enzymes are naturally occurring digestive enhancers that help animals make better use of feed nutrients. ChemGen is based in Gaithersburg, Md., and has manufacturing operations in Terre Haute that employ about 25 people.

Lilly is the world's 10th-largest drugmaker by annual revenue, according to the latest rankings from drug data firm IMS Health. The company lost the U.S. patent protecting its all-time best seller, the antipsychotic Zyprexa, from generic competition last fall and faces other patent expirations.

It has cited its animal health business as a key source of future revenue growth, along with its pipeline of drugs under development and sales in Japan and emerging markets like China.

Lilly shares climbed 16 cents, to $39.56 each, in afternoon trading.