Farmers are being reminded to ensure stock in paddocks next to roads or railway lines are securely fenced in to prevent them straying and being run down.
Seven cows had to be put down in the Waikato after being hit by vehicles early on Wednesday morning.
The seven were part of a group of about 30 that escaped from a farm and wandered on to the main road near Gordonton.
KiwiRail public affairs manager Kevin Ramshaw says there are one or two instances a week of stock straying onto railway tracks.
Federated Farmers dairy section vice-chairman John Bluett says road gates must be shut and road fences secure.
Mr Bluett says double-wiring gates is a useful precaution, as is having two gates between the stock and the roadside.
Federated Farmers says drivers travelling on back-country roads also need to be mindful of the dangers of wandering livestock.
It urges motorists to drive slowly, and not to sound their horns in case the noise spooks the animals.