Many breeds of domestic animal are threatened with extinction, according to the United Nations Food and Agriculture Agency (FAO).
It says the world is losing at least two breeds of animal every week.
The FAO keeps a register of more than 4,000 surviving breeds of domesticated animals and birds all over the world.
They include not only cattle, goats and sheep but also yaks, buffalo, ducks and even ostriches.
FAO experts say that 1,000 different breeds of domestic animal have become extinct during the past century and a third of surviving breeds are endangered.
Victims of success
The problem is the success of breeders in the developed world in exporting animals which have been bred to produce more and better meat or milk.
They go to developing countries where they may lack resistance to unfamiliar diseases.
Beata Sherf of the FAO explains: "We can't rely only on a handful of animals, because animal breeds are adapted to their special environments and if you transfer them to other environments they don't produce as well as in the environment they have been adapted to.
"You may just imagine a racing car ... on rough gravel roads. The performance would not be the same as on the racing circuit.
"And the same applies to animal breeds - if you transfer improved, highly productive breeds from developed countries into developing countries, with big stresses in terms of climate, disease and so on, these animals won't produce as in their country of origin."
Uncompetitive breeds
Even in North America, many breeds once considered valuable have been consigned to the "genetic waste basket", the FAO says.
Out of 259 breeds of animal recorded in Canada and the United States, more than a third are in danger of becoming extinct.
In Europe, a large number of breeds are endangered because farmers believe they are uncompetitive.
The poultry and pig industries are particularly relying on only a handful of specialised breeds.