A number of cows have been spotted stranded by landslides on the coast north of Kaikoura, following Monday's 7.5 magnitude earthquake.
The quake hit around midnight near Culverden, causing extensive damage to property, closing businesses and transport links and killing two people.
It could also be a season-ender for dairy farmers, who have already had to deal with drought conditions for years.
Federated Farmers' north Canterbury dairy spokesman Michael Woodward says milking sheds from the epicentre right up to Kaikoura have been damaged, with farmers unable to milk at all.
Those without power are choosing not to use back-up generators that run on water, because they need to conserve it for their stock.
Slips have also cut off tanker access to farms, meaning milk will be dumped because it can't be held in a vat for more than 24 hours.
Fonterra says disruption is expected to milk collection due to road closures at the top of the South Island.
It estimates around 30 farms in Kaikoura will not have their milk collected, and others around the country may have their collections delayed as tankers are rerouted