(Bloomberg) -- Pacific Investment Management, seeking to stem redemptions after its co-founder Bill Gross left unexpectedly, was dropped as manager of a $6.16 billion strategy offered by a unit of Prudential Financial.

Pimco, based in Newport Beach, California, will be replaced as subadviser of the AST Pimco Total Return Bond Portfolio by BlackRock and Loomis Sayles, according to a filing with the U.S. Securities and Exchange Commission yesterday. Pimco will also be dropped as manager of the U.S. fixed-income portion of the AST Advanced Strategies Portfolio, which had $8.75 billion in assets as of Sept. 30.

Prudential, the second-largest U.S. life insurer, didn’t say whether the decision was related to Gross’s move to Janus Capital Group on Sept. 26. Last month, a record $23.5 billion left the Pimco Total Return Fund, the world’s biggest bond mutual fund, which Gross had run. Former Pimco parent Pacific Life Insurance, Ford Motor, Massachusetts Mutual Life Insurance, Alabama’s Treasury and Florida’s state pension have all moved money away from Pimco in recent weeks.

Lisa Bennett, a spokeswoman for Newark, New Jersey-based Prudential, confirmed the filing and declined to comment further. Mark Porterfield, a spokesman for Pimco, didn’t respond to requests for comment.

The AST fund changes will take effect on or about Jan. 5, according to the filing. The Prudential managers will be Michael Collins, Richard Piccirillo, Gregory Peters and Robert Tipp, according to the filing. The Total Return fund will be managed by BlackRock’s Bob Miller and Rick Rieder, and Loomis Sayles’s Peter Palfrey and Rick Raczkowski.

'USUAL' BUSINESS

Pimco’s new chiefs are seeking to calm clients of the firm, saying there will be no major changes in investment strategy at the $202 billion Total Return Fund, the world’s biggest bond fund. They aren’t increasing cash-like holdings in the flagship fund to meet redemptions, Scott Mather, one of three newly appointed managers, said this month.

“It’s business as usual,” Mather said in a telephone interview last month after the management changes. “We’ve all been part of the team as members of the investment committee.”

BlackRock, the world’s largest money manager, is among beneficiaries of investor redemptions from Pimco.

BlackRock has attracted new client money this month as it benefits from a “team” approach and improved performance in its fixed-income funds, Chief Executive Officer Laurence D. Fink said.

'RELENTLESS FOCUS'

The firm’s “relentless focus on culture, the one BlackRock, a team approach is being highlighted quite a bit, but we have never changed our business model,” Fink said in a telephone interview on Oct. 15.

Since the 2008 financial crisis, BlackRock had been losing market share to Pimco as its funds underperformed. That trend started to shift as Fink, 61, reorganized the firm’s leadership to improve performance. About 87% of BlackRock’s fixed- income assets have beaten peers over the past three years, the firm said Oct. 15.

Gross built Pimco from a unit of the insurer previously known as Pacific Mutual Life Insurance into a $1.87 trillion giant. With his main fund trailing peers amid a record streak of redemptions, Gross left after his deputies threatened to quit and management debated his ouster, people familiar with the matter said at the time.

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