sheep at
Cregneash,
Isle of Man. There are fewer than 1,500 registered breeding Manx Loaghtan females in the
United Kingdom. There are several definitions of "breed" and "rare breed". Breeds may be defined as a group of animals that share visible characteristics, such as
Pinto horses, which are all spotted. A stricter definition insists that breeds are "consistent and predictable genetic entities", which means that individuals from that breed will produce offspring that is predictably similar to their genitors, and that this similarity is genetically based. This biological definition is useful for
conservation, which treats breeds as reliable sources of
genetic diversity. Conservation organisations each have their own definition of what constitutes a rare breed. The
Rare Breeds Survival Trust (RBST) and
The Livestock Conservancy (TLC) both divide rare breeds into five categories, "critical" being the rarest. TLC places a livestock breed under "critical" status when it has "fewer than 200 annual registrations in the United States and estimated global population less than 2,000". The RBST determines the status of a breed by the number of its breeding females in the
United Kingdom. For horses and sheep, fewer than 300 is considered "critical", whereas goats and pigs must have fewer than 100 to join that category.
The Poultry Club of Great Britain considers a poultry breed "Rare" when it does not have its own
breed club. These "Rare Breeds" are catered by the
Rare Poultry Society (RPS). The RPS does not look after breeds that count few individuals but have their own breed club. The
British Rabbit Council (BRC) notes in its breed standards those rabbit breeds that have been recognized by the affiliated Rare Varieties Rabbit Club, of which there are currently
26 breeds. ==Causes==