Let us not be shamed in having to depend on collecting crisp packets to pay for our children's schoolbooks.The series 'My Generation', written and presented by Joan Bakewell, starts on Sunday, BBC2 at 8pm. The Masai sheep herders of East Africa don't know it yet, but they are sitting on a genetic gold mine of benefit to farmers from Romney Marsh to Tasmania, the Welsh hills to the Falkland Islands. Their distinctive pure-bred sheep covered in red hair, a familiar site in the Rift Valley of Kenya, may soon prove to be the most valued rare breed of farm animals in the world. The Masai sheep herders of East Africa don't know it yet, but they are sitting on a genetic gold mine of benefit to farmers from Romney Marsh to Tasmania, the Welsh hills to the Falkland Islands. Their distinctive pure-bred sheep covered in red hair, a familiar site in the Rift Valley of Kenya, may soon prove to be the most valued rare breed of farm animals in the world. The "red Masai" sheep, one of the forgotten flocks of Africa, have an unrivalled resistance to the biggest scourge of sheep - the billion-dollar problem of intestinal worms. And geneticists in Kenya believe their resistance lies in a handful of genes that could be transferred into other flocks worldwide.

British veterinary scientists are watching their work with anticipation. So should hard-pressed British sheep farmers.And their story has a wider importance. The red Masai are a potent example of the hidden genetic value locked up in obscure animal breeds round the world, a "barnyard biodiversity" of growing importance as modern methods of fighting animal diseases falter. Saving them will help feed as well as clothe the world.For 40 years, farmers in rich countries have fought sheep worms with drugs. But, says Leyden Baker of the Nairobi-based International Livestock Research Institute (ILRI), "the resistance of worms to the drugs is growing. We could soon be losing 30 or 40 per cent of wool and meat production because of premature deaths and sickness."The drugs are the internal counterpart to chemical sheep dip, which attacks infestations in sheep fleece.

And, like sheep dip, there are also growing environmental and health concerns because the drugs tend to build up in meat and pastures. For such reasons, ILRI has spent a decade searching for an alternative to the drugs by scouring Africa for native breeds of sheep that show the strongest genetic resistance to the worms. Two years ago, they settled on the red Masai."It is a remarkable animal," says Michael Stear of Glasgow University's veterinary school. "The red Masai thrives in conditions that would kill many other sheep breeds." In particular, it shrugs off a virulent African worm called Haemonchus contortus that sucks blood from the gut, leaving other sheep sick and anaemic.Despite its unique attribute, there hasn't been a rush to add the Masai sheep to flocks round the world because of an equally obvious disadvantage They grow hair and not wool.