Bega Cheese executive chairman Barry Irvin is extending his leave by six months as he undergoes chemotherapy.

The dairy processor says Mr Irvin has appointed long-time director Max Roberts as his alternate director and chairman in his absence.

Bega announced last month that Mr Irvin would step aside to recover from surgery but gave no further details.

In an update on Monday, the company said Mr Irvin’s chemotherapy was to treat the cancer that had been dealt with in his surgery.

Mr Irvin became chairman of the Bega co-operative society in 2000 after returning to the dairy industry from a stint in finance.

He has been executive chairman of Bega Cheese since 2008 and was at the company’s helm when it listed on the ASX in 2011.