In situ conservation of livestock and poultry
by Elizabeth L. Henson
3.3.1 Unique Populations
'Uniqueness is difficult to define with respect to livestock populations. There are clearly some populations with obviously unique characteristics or traits. For example naked neck chickens (Bodo et al, 1990), seaweed eating North Ronaldsay sheep (Henson, 1978), or the Kuri cattle of Lake Chad whose hollow horns enable them to swim to the lake islands (Adeniji, 1983). There are also breeds or strains which exhibit extremes of quantitative production traits for example, the miniature Dexter cattle of Ireland (Ark, 1976), the prolific Taihu pigs of China (Peilieu, 1984), and the excessively fat Mangalitza pigs of Hungary (Baltay, 1982).
For the vast majority of populations their uniqueness is subjective. It refers to the fact that no other population has the same ancestry, environmental adaptation, human selection, appearance or production characteristics. In effect, the difference between two populations may only be a function of the relative frequencies of the same genes. From the point of view of conservation any population which is historically or geographically isolated or which has had little genetic influence from other breeds over a long period of time, or which exhibits unusual characteristics or traits should be considered to be a unique population.'