Utilisation and conservation of farm animal genetic resources 139
Chapter 6. Selection of breeds for conservation
only to proportionality Bennewitz et al., 2006. When, in addition, the loss of within
breed diversity will be considered, estimates of the efective population size are required for the quantiication of the expected drit. It should be noted that the breeds selected
for conservation based on their conservation potentials are not necessarily the most endangered breeds, making the results of the maximum-diversity-strategy diferent
from the risk-strategy. For example, the correlation between the extinction probabilities and conservation potentials was only around 0.4 in the study of Bennewitz
et al. 2006, involving 44 North Eurasian cattle breeds. In Box 6.4 an example of the results of the
maximum-diversity-strategy is presented.
Box 6.3. he extinction probabilities of breeds. he extinction probability of a breed is deined as the probability that a breed will go extinct at
some point within a deined future time horizon e.g. 25 or 50 years. he problem in modelling, and consequently in estimating these probabilities, is that extinction of a breed is a rare event and
therefore any model validation and formal model comparison is almost impossible. A semi-quantitative method was applied to a set of 49 African breeds by Reist-Marti
et al. 2003. hese authors scored the breeds for four variables related to the population population size and
its change over time, distribution of the breed and risk of discriminate crossing, four related to the environment organisation among farmers, existence of a conservation scheme, political
situation and reliability of the information and two related to the value of the breeds presence of special traits and cultural value. he extinction probabilities of the breeds were calculated as
the sum of the 10 variables and were re-scaled to a value between 0.1 and 0.9 in order to prevent extreme probabilities. Probabilities of zero and one were not allowed, because the future cannot
be foreseen. his approach is appealing, because of its comprehensiveness. Simianer 2005b argued that the extinction probability of a breed is directly related to the rate of
inbreeding. Following this, he obtained extinction probabilities as 12
N
e
and multiplied them by a constant to obtain reasonable values. herefore these probabilities can be interpreted as relative
rather than absolute probabilities. he same holds true for the estimates obtained from the Reist- Marti method. he problem of these two methods is that they do not produce any standard errors
or conidence intervals of the extinction probabilities. A quantitative method adapted from conservation biologists was used by Bennewitz and
Meuwissen 2005. his method is based on a time series approach and involves a random process to predict likely future population size based on recent census data. On the one hand,
the method produces absolute rather than relative extinction probabilities and also conidence intervals for the probabilities. However, the extinction probabilities were either close to zero or
close to one and the conidence intervals covered almost the whole parameter space. he reason may be, that this method is tailored to wildlife populations, which show much greater amplitudes
in population size over time.
140 Utilisation and conservation of farm animal genetic resources
Jörn Bennewitz, Herwin Eding, John Ruane and Henner Simianer
Although conservation potentials are very useful for prioritising, they do not tell us anything about the optimal allocation of the budget with respect to maximising the
conserved diversity. For the optimal allocation of the budget, the analysis has to involve a cost function for the reduction of extinction probabilities of the breeds Weitzman,
1993; Simianer, 2002; Simianer
et al., 2003. More precisely, this method assumes that marginal costs and marginal returns in diversity of conservation activities can be
speciied for each breed. he total budget available for conservation is then allocated over the selected breeds using an iterative algorithm in order to maximise the conserved
diversity. See Box 6.5 for further details of the optimum allocation approach.
An alternative to the use of conservation potentials is the so-called ‘safe set+1’ approach as used by haon d’Arnoldi
et al. 1998 and Eding et al. 2002. Following this, a safe
Box 6.4. Example of the application of the maximum-diversity-strategy. Bennewitz and Meuwissen 2006 used a small data set consisting of nine Dutch cattle breeds
genotyped for a number of microsatellite markers to demonstrate the maximum-diversity-strategy. hey used the Maximum-Variance-Total core set diversity measure chapter 5. he marginal
diversities md considered the expected loss of between breed diversity due to extinction of
breeds and the expected loss of within breed diversity due to drit. he prioritising of breeds for conservation could be done accordingly to the conservation potentials
CP.
Breed Efective
population size
1
Extinction probability
md
i 2
CP
i 3
Belgian Blue 370
0.027 11.14
0.301 Dutch Red Pied
68 0.147
34.17 5.023
Dutch Black Belted 154
0.065 32.22
2.094 Limousine
400 0.025
154.74 3.869
Holstein Friesian 1000
0.001 23.61
0.024 Galloway
23 0.435
190.48 82.859
Dutch Friesian 294
0.034 5.82
0.198 Improved Red Pied
111 0.090
41.77 3.759
Blonde d’Aquitaine 217
0.046 8.31
0.382
1
he efective population sizes were taken from the database of the EAAP.
2
md describes how much the expected future diversity would change with respect to a small reduction in a breed’s extinction probability.
3
CP describes how much the expected future diversity would change if a breed was made completely safe, i.e.
CP = md × extinction probability.