Molson Coors Brewing Co.'s (TAP) first-quarter earnings more than doubled as the beer maker increased prices and benefited from its new U.S. joint venture.

The company's newly formed joint venture with SABMiller (SAB.JO), MillerCoors, continued to achieve cost savings faster than planned and reported a 51% jump in first-quarter earnings on a pro-forma basis. Molson Coors shares were recently up 12% to $43 as earnings beat expectations.

By the end of this year, MillerCoors expects to achieve $238 million in cost savings, surpassing its original forecast of $225 million. On a conference call, Molson Coors said the joint venture grew sales to retailers at a low single digit rate early in the second quarter.

The company's U.K. operations continued to stay weak as volumes fell in the region due to continuing weakness in the economy, contributing to a 2.7% drop in global beer volume. In an interview, Chief Executive Peter Swinburn said the company doesn't expect a major turnaround in that business in the short term, but added that the company is feeling more "confident" in its outlook for the U.K. operations as it has raised prices and invested in its brands.

Molson Coors' first-quarter earnings were $75.7 million, or 41 cents a share, compared with $34.3 million, or 19 cents a share, a year earlier. The results included losses from discontinued operations of 2 cents and 5 cents, respectively. Net sales fell 59% to $559 million because of the MillerCoors venture.

The mean estimate of analysts surveyed by Thomson Reuters was for earnings of 33 cents a share and revenue of $568 million. Swinburn said some of the company's cost savings came from improved negotiations with its suppliers.

In Canada, home to the Molson brand, pretax profit fell 9.4% as volume was flat.

(Kevin Kingsbury and Kerry E. Grace contributed to this article)

-By Anjali Cordeiro; Dow Jones Newswires; 201-938-2408; anjali.cordeiro@dowjones.com