Ares Management of Century City on Thursday announced its purchase of National Veterinary Associates in Agoura Hills.

The private equity firm bought NVA from funds affiliated with Summit Partners, which has offices in Boston, London and Menlo Park. NVA’s senior management will retain a minority stake.

Terms of the purchase were not disclosed. The transaction is expected to close in the third quarter of the year.

NVA has more than 240 animal hospitals operating in California and 38 other states. The company was founded in 1996.

Jefferies, a New York investment bank, was National Veterinary Associates lead adviser for the deal.

The announcement was made after markets closed. Ares Management’s share price had fallen 6 cents, less than a percentage point, in Thursday’s trading to close at $19.02 a share on the NYSE.