The five-year-old pedigree was discovered by farmer Hugh Passmore while he carried out his daily morning checks at Applesham Farm, in Coombes.
It is believed a dog carried out the attack which left the sheep with a six-inch gaping wound across the back of its neck, a badly bitten leg and missing an ear.
Mr Passmore said: “The wounds were horrendous. It was sickening really.
“As I went to check the sheep, they were all bunched up in the corner of the field and I knew something was wrong. I then found the ewe, which had been attacked. She was still alive, but the back of her neck had been ripped out by the dog.”
Tim Potter, from Westpoint Farm Vets, attended the farm but after examining the ewe decided that it had to be put down.
Mr Potter said: “The attack was particularly savage, with multiple severe wounds consistent with dog bites. The ewe had one ear missing and a six inch deep wound stretching right round the back of her neck. Unfortunately we had to put her down.”
Following the attack Mr Passmore checked the ewe’s records and discovered that it was one of his better livestock.
He said: “She was a pedigree. She had produced some good lambs.
“There’s the cost of replacing her, and I’ve ended up with a large vets bill for it. That wasn’t my concern at the time, it was her welfare because of the state she was in.”
The National Farmers Union (NFU) is warning dog walkers to keep their pets under close control when walking in the countryside following the gruesome attack.
There were no witnesses to the attack, so Mr Passmore is doubtful that the police will be able to locate the dog or its owner.
James Osman, NFU Sussex County Adviser, said: “The vast majority of dog owners and walkers are considerate, but we are very concerned at the rising number of attacks on livestock by dogs that we hear about from farmers.
“Even if dogs don’t physically attack livestock, chasing them can cause pregnant cows and sheep to abort or lead to panicked stock getting tangled up in fences.”
Figures from Sussex Police show that there were 121 recorded cases of livestock worrying in 2014.
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