Sheep rustling has risen fivefold in just over a year, with farmers and police complaining of organised gangs adept at handling livestock.
The soaring price of lamb combined with the recession have made the woolly animals a prime target for thieves. Across the country police forces have complained of gangs targeting farms, on some occasions leading away hundreds of animals.
"In the last 18 months we have seen the number of rustling thefts from farms increase fivefold," said Tim Price, a spokesman for NFU Mutual, which insures two-thirds of farmers. "We have had about 10 years at a very low level and it has taken off again.
"We think there are two factors: the price of meat has shot up, and the recession. In the past when there is a downturn in the economy, rural crime goes up."
With the price of lamb rising from £2.70 to £4.80 a kilogram, the average animal now sells for about £65, nearly double the price it fetched three years ago. The weak pound also means sheep are being exported and thieves, who in recent years reacted to global price rises for metal by stealing scrap, and for oil by raiding farm tanks, have now turned their attention to another source of income.
Counties such as Northumbria have been hit particularly hard, with police appealing for help from the farming community after a total of 411 sheep, worth more than £25,000, were stolen in nine separate incidents in the past few months.
North Yorkshire and North Wales have suffered a spate of thefts in recent weeks. Last month West Mercia Police said 161 animals had been taken in 2009-10, double the number stolen the previous year.
Cumbrian officers said they were seeing incidents on an unprecedented scale, including the theft of 100 breeding sheep worth £10,000 in September. Farmer Andrew Allen, who had 45 Swaledale ewes stolen in the same month, said he was "angry and gutted". He added: "Whoever took the sheep must have had a decent dog and be used to handling stock."
PC John Baldwin said: "Before you would get thieves stealing a small number of sheep – 10 or 15 or so, which could be slaughtered in a back garage and the meat sold to friends or work colleagues. But now it is many more. On this scale it must be being done by well organised gangs who have a working knowledge of animal husbandry."
In one of the worst cases this year, 271 Texel sheep were taken from a farm in Lancashire by raiders who herded them through a pen and on to a truck.
Mr Price of NFU Mutual said animals had even been butchered in the fields, warning people to be wary of bargain meat that may not have been hygienically slaughtered. The insurer urged people only to buy from reputable sources and to look out for suspicious night-time activity on farms.
The NFU Livestock Board's chairman, Alistair Mackintosh, said yesterday that such thefts came in spates. "How do you guard a whole farm?" he said. "That is the vulnerability of farming. Very often it is almost a lifetime's work breeding these sheep with pedigrees and it is heartbreaking to see that work devastated. All the farmers I know are vigilant but when the sheep are out in the fields at night it is very difficult to keep the same degree of security."