Emergency semen supplies have been flown in for flood-hit South Island dairy farmers as roading damage disrupts deliveries during a critical time in the farming calendar.

Farmers in south Canterbury and parts of the West Coast have been hit hard by the flood event, with damage also sustained to key roads and highways.

The floods have hit during the critical spring mating period for most dairy farms and the disruption meant it had been difficult for some farmers to get their cows in calf.