When Sue Pye poured blue top Value milk into her coffee and took a taste she was disgusted.
The milk had a faint taste like the smell of silage in a paddock. It was gross, she said, but the taste was different from milk that's "off".
She took the bottle back to Whanganui's Pak 'n Save, where she was offered a refund or an exchange.
Staff at the store told her she wasn't the only one who found the taste unpleasant and asked for a substitute.
She exchanged the bottle for an Anchor blue top, only to find that too tasted "not that nice".
A spokeswoman for the owners of Pak 'n Save and New World said the milk was not unsafe, and the strange taste was "a quality issue" rather than a food safety issue.
The problem affected only Anchor blue top 1 litre and 2 litre milk and Value standard 1 litre, 2 litre and 3 litre bottles of milk - and only those with best before dates from 22 to 27 June, inclusive.
Only supermarkets in the lower North Island were affected. They have now restocked with other milk.
The different taste may have been caused by a change to the cows' feed, she said.
"This does happen on occasion."
The milk came from plants managed by Fonterra.
Fonterra recalled the milk from a number of North Island supermarkets.
"We've removed the dark blue top milk we know to be affected from our supply chain and we're working hard to get replacement stock back on the shelves," Managing Director of Fonterra Brands New Zealand, Leon Clement said.
In a statement late on Friday Fonterra said that it had conducted a thorough investigation, which clearly points to the unusual taste being due to feed.
Brassicas - a vegetable plant family that includes turnips and swedes - are fed to cows at this time of year, Fonterra said, and when they eat too much, it can affect the taste of their milk.