States vet Linda Lowseck and shepherds Ewen Hare and Aaron Le Couteur are urging Islanders to be more vigilant after the grazing animals were set upon in a field at Beauport earlier this week.
Among the wounded sheep, which belong to Mr Le Couteur but are used under a joint venture with the National Trust for Jersey, was a one-year-old animal named Bercail Gallant, who sustained a serious wound to her rear left leg which needed stitches.
It is not known what type of dog was involved, but Mr Hare said that a large animal was suspected, given the nature of the wounds.
The attack follows another in which a greyhound was left with deep bite marks in its legs from what was thought to be a Staffordshire bull terrier last week.
