Agriculture Minister David Carter says 'dirty dairy farmer' Allan Crafar could do huge damage to New Zealand's reputation.

Fonterra says it won't hesitate to take action, "including refusal to collect milk" if deliberate animal mistreatment is proven.

New Zealand's biggest privately held dairying operation allowed dozens of calves to slowly dehydrate to death.

Test results due back today may point scientists towards the cause of the mystery illness or illnesses affecting dogs and wildlife in the Hauraki Gulf.

Researchers believe they may be dealing with two or even three unrelated causes of illness in the Hauraki Gulf.

Health authorities have issued an alert for all eastern Auckland and Hauraki Gulf beaches after two dogs died and others fell sick.