Pressure groups claim that lambs - the only remaining farm animals to carry an image of countryside freedom - are now being factory-farmed indoors in Britain, fed on pellets instead of grass, thanks to an artificial hormone which induces ewes to give birth outside the normal spring lambing season.
The development, still in its early stages, has been facilitated by the drug melatonin, which fools ewes into having lambs in the winter rather than the spring, and enables them to have an extra lamb every two years. It was licensed by the Ministry of Agriculture four years ago.
The lamb campaign will put new pressure on the Agriculture Minister, William Waldegrave, who came under widespread attack last week after the Independent on Sunday revealed he was selling calves from his dairy herd to be reared as veal in Europe in the type of crates his own ministry banned for their cruelty in 1990.
Today animal rights activists, environmentalists and protesters against the Criminal Justice Act intend to hold a mass trespass at Mr Waldegrave's farm at Chewton Mendip, Somerset.
Farmers, eager to get good prices after the abolition three years ago of an EU subsidy for each slaughtered lamb, are increasingly turning to melatonin, because the winter lambs it enables ewes to produce can be slaughtered in the spring, when the price of lamb is higher and British sources are scarce.
The method is widespread in the Netherlands and Australia. Such British retailers as J Sainsbury are already buying lamb produced in this way.
But campaigners say it is cruel and leads to factory-farming. "We are not talking about some of the farmers who bring sheep into barns to lamb in bad weather, we are talking about intensively reared lambs fed on pellets in a creep [a wooden stall], " said a spokesman for the group Animal Rescue, which is leading the new campaign. "Our concern is that lambs are going the same way as veal."
Edward O'Hara, Labour MP for Knowsley South, is asking Mr Waldegrave to ensure that use of the drug spreads no further.
"The fact that you can force ewes to have three breeding cycles in two years means that they are becoming production units on a factory bench," he said.
Vets and animal welfare groups warn that raising dozens of lambs and ewes together in barns - where the lambs are fed concentrate pellets to increase their weight quickly - can lead to disease and behavioural problems. Forcing ewes to produce an extra lamb every two years,they say, could damage the animals' health and perhaps prove fatal.
"If the lambing is brought forward to November or December it must be brought inside," an RSPCA spokesman said yesterday.
"Disease will whizz round if they are in close proximity, and lambs can easily get crushed. Lamb until now has had quite a well-deserved `green' image. It is the only animal to have escaped intensification."
Militant animal rights campaigners have sent threatening letters, some containing razor blades, to Mr Waldegrave. The letters were posted to his West Country home and his London office.
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