In the latest incident, a 15-month-old relative of champion Black Caviar was shot through the chest in a Springbank paddock on January 13.

The Ronan family farm is flanked on three sides by land owned by Central Highlands Water (CHW), which has used hunters to control vermin and has assisted police with a previous investigation into shootings on the Ronan family's property.

Police said the unnamed filly was killed by a high-calibre rifle on the Simpson Road property about 10pm.

They are unsure whether the horse was deliberately shot or whether the death was a case of mistaken identity.

The filly's mother, Palace Beat, is a full sister to the mother of champion racehorse Bel Esprit, the sire of unbeaten mare Black Caviar.

Paul Ronan, devastated by the death, raised concerns that CHW employees were letting "spotlighters" onto Crown land, who might be shooting into nearby properties.

"They used to come with 10 car loads of shooters every weekend, hunting dogs and everything," he said.

Mr Ronan said the shootings petered away after a police investigation more than 18 months ago but had resumed in the past three weeks.

His brother, Gavin Ronan, pleaded with shooters to stay away from the property, where he lives with his two children under five years old.

A CHW spokeswoman said it had used licensed "vermin control contractors" on its properties to shoot feral animals in the past.

But the spokeswoman said no contracted shooting had occurred on those properties for more than two years. She said when it did, neighbouring landholders and local police were informed beforehand.

"We've co-operated with police, and it is a police matter," she said.

Bacchus Marsh's Detective Senior Constable Brian Malloch said investigations were continuing.

He said CHW was "doing its best to combat" the violent acts.

"They have banned all shooting on that patch of land, and CHW employees are helping with investigations."

Information to Crime Stoppers on 1800333000.