The so-called Lion Man, Craig Busch, has failed in a court bid to take back control of his business.
Mr Busch is locked in a dispute with his mother and applied to Whangarei High Court for an interim injunction to stop her controlling his companies.
Patricia Busch mortgaged her farm for $1.7 million in 2006 to pay her son's personal and business debts.
In exchange, she took over as sole director of Zion Wildlife Gardens and sacked Mr Busch, replacing him with a qualified zoo manager.
On Thursday, Justice Heath said Mrs Busch's investment in her son and his companies could not be justified on commercial grounds.
The judge said Mr Busch could regain control of the business if he is able to borrow enough money to buy back his shares.
He urged the mother and son to go to mediation and discuss their options.
Mr Busch is also challenging his mother in the Employment Court over his sacking in November.