Police said an ‘unknown substance’ was added to the cows’ water and that they were treating the incident as suspicious.
The dead cattle were discovered on a farm near the village of Ham, on the Wiltshire-Berkshire border, near Hungerford. It is thought they were poisoned sometime between April 27 and 28.
Officers have appealed to the local farming community via text, asking for information.
John Bordiss, police community support officer with the Wiltshire Rural Crime Team, said in a community alert: “Between 27 and 28 April an unknown poisonous substance was added to water troughs within an open barn containing 67 in-calf beef cattle.
"By Friday morning 10 were dead along with unborn calves. Clearly upsetting for all involved.”
Wiltshire Police are appealing for anyone with information to come forward by calling 101 or Crimestoppers on 0800 555 111.