The Fukushima Prefectural Government has finished culling 1,692 abandoned cows in the 20-km radius hot zone around the Fukushima No. 1 nuclear plant, prefectural officials said Wednesday.

About 3,500 cows owned by 315 livestock farmers were in the area before the March 2011 Great East Japan Earthquake and tsunami triggered the nuclear disaster, they said.

In May 2011, the central government called for the culling of Fukushima livestock and poultry in the exclusion zone with owners' consent because the radioactive fallout was preventing them from being fed.

Between 10 and 20 farmers who opposed the culling are still breeding around 750 cows in the area on condition that any related produce is not sold on the market.

Some are helping to conduct research on how the radiation is affecting the cows and on whether their feeding is aiding decontamination efforts.

Keiji Okada, an associate professor at Iwate University who is heading the research, said, "We hope we can get a result that contributes to society."