Shares in Macquarie Fortress Notes dropped 56 per cent on Monday after the investor in high-yield products was forced to sell some US debt investments at a loss after breaching bank covenants.

Macquarie Fortress Notes, which is managed by a Macquarie Bank-controlled entity, is one of a trio of funds that raised A$230m (US$207.8m) of equity to invest in US dollar-denominated senior secured corporate loans.