The attack took place between April 30 and May 1 during the bank holiday weekend.
Sussex Police Rural Crime Team said the dogs had to be shot to protect the flock.
The dog owner agreed to recompense the farmer after the attack
South Yorkshire Police have warned irresponsible owners are endangering livestock.
A man has been charged after 93 pregnant sheep were chased by a dog near Auchterarder in Perthshire.
A ewe and 21 lambs have been killed after two dogs were let loose in a field in Kent.
A dog owner on the Isle of Wight has paid £300 in compensation following the death of a sheep in a livestock worrying incident.
Significantly tightened legislation seems to be doing little to prevent free running dogs attacking sheep in Scotland.