A veterinary group in the United Kingdom that mushroomed within four years from one to 87 locations is the latest acquisition of Mars Inc., the largest owner of veterinary practices in the world.

Mars Petcare announced Thursday that it intends to buy Linnaeus Group Ltd. from Sovereign Capital Partners, a private-equity firm. The companies did not disclose the sales price.

However, Sovereign called the sale its "largest ever," declaring in a news release that the transaction would "generate Sovereign's strongest ever gross return."

The Linnaeus Group was started in September 2014 with an investment by Sovereign in Willows Veterinary Centre and Referral Service in Solihull, West Midlands, which is roughly 100 miles northwest of London.

"Sovereign recognised the opportunity to undertake a significant Buy & Build strategy and create a market-leading veterinary group," the news release reads.

In fewer than four years, the group grew to 87 sites in England, of which five are specialist referral centers. Its workforce numbers 1,400, including 360 veterinarians, according to the statement.

Mars Petcare, in its announcement, describes Linnaeus as "an innovative provider of veterinary services [that] offers an outstanding referral-led hub-and-spoke platform in the UK." The hub in the metaphor is the specialist hospital, and the spokes are primary-care clinics.

Mars Petcare has been in the veterinary-clinic business since 1994, when it acquired an interest in Banfield Pet Hospital, a practice chain based, at the time, in Portland, Oregon. (Banfield has since moved its headquarters to Vancouver, Washington.) Mars later assumed full ownership of Banfield, the country's largest veterinary-clinic operator.

Mars began buying other veterinary-practice brands in 2015 with the acquisition of BluePearl, a chain of specialty and emergency hospitals founded in Florida. The following year, Mars bought Pet Partners, a chain based in upstate New York.

In 2017, Mars shifted the landscape of veterinary-practice ownership in the U.S. with the purchase of the country's second-largest practice operator, VCA Inc. That transaction put more than 2,000 locations under a single owner.

According to its news release about Linnaeus, Mars Petcare today employs some 50,000 veterinary professionals and cares for more than 10 million pets a year.

In addition to veterinary hospitals and clinics, Mars Petcare owns multiple pet-food brands — Pedigree, Whiskas, Royal Canin, Nutro, Sheba, Cesar, Iams and Eukanuba — among other products for pets. By acquiring VCA, Mars Petcare also became the owner of Antech Diagnostics, one of the largest veterinary laboratories in the U.S.; and Sound, a major purveyor of veterinary medical equipment.