Fonterra said its milk production hit a seasonal high of 86.9 million litres on October 22 - down 3 per cent from last season's peak.
The co-op said five new plants each contributed to a record amount of "peak" milk made into value-added products this month.
Managing director global operations Robert Spurway said the additional capacity had given the co-operative more options with its product mix.
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"Getting the most out of large volumes comes down to having the capacity to process every drop of our farmers' milk while also striking the right balance between our ingredients and foodservice capabilities," he said in a statement.