Farmers are being warned to check fences on their properties in the wake of an increase in the number of wandering stock on the country's highways.

The New Zealand Transport Agency says a horse was hit by a vehicle in the Bay of Plenty this week.

The driver was unhurt but  the horse had to be put down.

The agency's Bay of Plenty state highway manager, Rod James, said in another case 30 cows got loose, posing a serious risk to motorists. He says animals in drought-hit pastures may be seeking more feed, and he's asking farmers to check fences on paddocks near state highways.