Cattle shot near National Park in the Ruapehu District on Wednesday had been wandering in the Tongariro National Park for two years.
The Department of Conservation says the animals escaped from a farm that borders the park and efforts since to find them failed.
It says the cattle, thought to number about 13, originally escaped through a broken fence and have since been grazing in the park.
DoC says seven of the animals were finally rounded up this week and there was no alternative but to destroy them as they were a danger to traffic on State Highway 47.
The department says since they escaped at least two were shot wandering on roads and four were hit by vehicles, including two in the past week.
DoC says it is the responsibility of farmers to fence national park boundaries, but once animals get into a park it is the department's responsibility to remove them.