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
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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.
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