Six sheep were killed when they were forced into a river by a dog on the Earth Trust Farm in Little Wittenham, Oxfordshire.
The animals were pulled from the River Thames on Thursday the 8th of September.
Five had already drowned and a sixth succumbed to shock and water inhalation overnight.
Shepherd Emma Blomfield said she was "devastated to have lost so many animals in one day".
The Earth Trust has urged people passing through the field at the foot of the Wittenham Clumps to keep their dogs on a lead. About 200 sheep and 25 cows graze there.
Earth Trust Farm manager Chris Parker said: "It’s very distressing to see animals killed in this way, especially when the accident was completely avoidable.
"There are signs at every entrance to the meadow asking dog owners to keep their dogs on a lead whilst sheep are in this field.
"This is the second time in a week that sheep have been pulled from the river after being chased by dogs and, sadly, this time there were tragic consequences."
