The significance of Original Populations in native livestock conservation: A personal view

Prof. Tim Morris

The launch of the 2021 Rare Breed Survival Trust (RBST) Watchlist represents a further evolution of how the RBST prioritises its work on livestock breed conservation. Previously the Watchlist used just the numbers of breeding females, it now also factors in the degree of inbreeding. This is because it is no use having larger breed numbers, but all with a high degree of inbreeding. Likewise with only a very few examples of a breed, then the degree of inbreeding is a moot point.


There are four sheep breeds, two goat breeds, five-six cattle breeds, six pig breeds, and seven equine breeds defined as ‘Priority’ by this new Watchlist methodology (it is not used with poultry). Why are they are a ‘Priority’; because there is a danger that without action they might be lost. So with this new more robust prioritisation methodology, the RBST can really focus its work. I say ‘five-six cattle breeds’ because one is actually the Original Population Dairy Shorthorn. This is not to single out this Original Population, RBST also lists several others.


So what is an Original Population? Both the UK Government and RBST have a similar definition that addresses the situation where an established native breed has been managed in a way that threatens its native status or, in more extreme cases, its very status as a breed. This can arise when a breed undergoes significant genetic introductions (introgressions) from animals of the same breed born outside the UK, or from animals of a different breed, such that it results in the loss of its native status.


The crux of this dilemma on separating out Original Population is, for me, the word “significant”. Those advocating Original Populations in an RBST context have tended to focus on the differences within a breed. But are those differences so ‘significant’ that the parent breed has actually now become a distinct non-native breed? Whilst the phenotype of this parent breed and proposed Original Population, how the two populations perform and especially how they look, might be similar or dissimilar, there are dangers in relying on appearances - as shown with the (in)famous completely unrelated lookalikes in Private Eye; ’perhaps they are related?’.


It is possible to analyse data from herd and flock books, but their accuracy is ultimately dependent on the accuracy of information independently submitted over many years. There is instead a transparent truth in genomic assessment of breed identification; it can both clearly differentiate breeds but also clearly identify introgressions from other breeds. There are some examples of genomic assessment of original populations, for example in cattle. For me, whilst this leaves open the question of ‘significance’, with genomic analysis now being routine, genomics should be an essential component of the initial assessment of a putative Original Population.


But beyond this genomic assessment of significant introgression we must also recognise the context that the RBST’s objects include the preservation of agricultural breeds or populations having characteristics worthy of preservation; they are ‘there for a reason’. Breeds were selected over populations as the focus on conservation by the RBST’s founders because of both their genetic value in the past or future, as well as their intrinsic value, in particular they had been selected for a reason and/or locality. (In terms of ‘populations’, the focus of RBST’s founders was on ‘feral’ populations, i.e. populations without the more formal records that characterise a breed).


Therefore a starting point to consider this RBST-focused aspects of Original Populations is both any characteristics worthy of preservation and those characteristics within their whole breed population. Are those specific characteristics of the possible Original Population both worthy of preservation and if so, are they so ‘significant’ that they require separate categorisation and prioritisation from other characteristics of the parent breed?


The challenge with Original Populations is therefore not in itself scientific or technical, as noted genomic assessment is widely available. The challenges are: semantic, what is ‘significant’; informational, with little or no systematic collection of relevant genomic and performance data for parent Breed-Original Population comparisons; but also social.


The contribution of human element has been under estimated in these discussions. There is increasing interest in the role social practice has taken in developing livestock breeds, and so we should not neglect understanding the role of the human animal, rather than the non-human animal, as we consider and possibly categorise Original Populations of livestock breeds.