Ibbotson Associates has replaced Vanguard Investments as the underlying investment manager for the $222 million Ibbotson Australian Bonds Trust with Omega Global Investors.

The appointment of the new managers means the Australian Bonds Trust moves from being a passively-managed government bond-only vehicle to an enhanced passive composite strategy, which invests in both Australian government debt and high-quality Australian corporate debt.

"The continual review of investment managers is fundamental to Ibbotson's investment process, and changes are designed to best capture the current prevailing market opportunities, while also seeking to improve future returns," the firm said.

Ibbotson, which provides asset allocation, manager selection and portfolio construction services, is wholly owned by Morningstar.

Omega utilise an enhanced index strategy to avoid the large exposure to Australian bank issued securities that is a feature of the UBS Australian Composite Bond Index.

Omega was established in 2008, and is a fixed-income boutique majority-owned by its principals.

The investment team is jointly headed by Omega investment directors Matthew McCrum and Andrew Gruskin.

McCrum was previously head of fixed interest at Vanguard Investments, while Gruskin worked for Alpha Investment Management and was responsible for quantitative portfolio management and analysis.

Macquarie Global Investments owns 19.90 per cent of Omega.