A company trialling virtual fencing for cows in Otago using electronic collars says tests show encouraging results.

Pāmu Farms, which is the brand name for state-owned enterprise Landcorp Farming Ltd, earlier this year trialled "e-Shepherd" cattle collars at Waipori Station, which it owns.

It took 100 Angus steers equipped with solar-powered collars that show their location through GPS.

When the animals moved near digitally set forbidden zones they were dissuaded with a buzzing noise which gradually grew louder.

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If this did not work, the animal received a single electric "pulse" to the back of its neck.

The five-week trial starting in February was led by AgResearch senior scientist David Stevens and assessed how stock reacted to the training and boundary controls of virtual fences.

Pāmu has now released highlights of the trial results.

A Pāmu spokesman said the findings were "encouraging".

The trial observed all animals responded to audio boundaries with minimum effect and none displayed any adverse effects as a result, he said.

There was no difference in live-weight gain or condition score between control and trial mobs.

Animals also retained normal behaviours such as resting at the highest point of the paddock, regardless of proximity to the virtual fence.

A further trial at Lake Mahinerangi would test the solar recharging capacity of the collars and remote base station over the low-sun winter months.

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The trial included weekly independent veterinary and welfare inspections, assessment of live weight, body condition scoring and visual observations, as part of the strict criteria outlined by AgResearch's animal ethics committee, the spokesman said.

"This trial is part of Pāmu's ongoing assessment of the latest innovations to improve both animal welfare and environmental footprints on our farms."

The idea of the devices is partly to aid large farms for which the cost of fencing is prohibitive.