Verena Gonzalez Lopez, 2011 - Institut für Tierzucht und Tierhaltung ...

In the present study, optimum contribution theory was applied in a small pig
herdbook population. In order to ensure that the different scenarios investigated are
close to practical breeding schemes, specific conditions determined from the local
breeding organization were considered. First, a predefined number of 50 elite sows
should be selected. Moreover, a preselection of candidates has been carried out
based on minimum performance requirements. This was necessary to ensure that
progeny of elite matings can also be sold to potential customers such as artificial
insemination organizations in Germany. Indeed, a considerable number of animals
with high EBV and low relationship value were discarded during the first selection
step. The main criterion causing the loss of potential candidates was the restriction
on carcass length.
Applying the optimum contribution selection, the number of animals selected
increased and the average expected breeding value of selected animals decreased
the more the relationship was constrained. These results were consistent with those
of Weigel and Lin (2002) and König and Simianer (2006). The relation between EBV
and optimized contributions with different constraints on relationship observed in this
study was in accordance with other studies as well (Grundy et al., 1998; Avendaño et
al., 2003). In addition, it was demonstrated that a higher average breeding value of
selected animals could be achieved at a severe relationship constraint by considering
boars from BW. This can be explained by the fact that BW boars had a lower
average R-value to potential candidates compared with SH boars. For this reason,
the largest proportion of selected boars composed of BW boars (Figure 4 and 5).
Individual BW boars were also highly related to the potential SH candidates as a
result of exchange of genetic material between herdbook populations in past
decades (Gonzalez Lopez et al., unpublished data). Therefore, a targeted application
of BW boars is recommended.
After the selection of elite sows and boars by applying the optimum contribution
selection, minimum coancestry mating with linear programming technique was
applied to define the specific mating between sows and boars. This two-step
selection and mating strategy requires less computer time, compared to a one-step
selection and mating scheme, for example the linear programming algorithm of Toro
and Pérez-Enciso (1990) which have to include all selection candidates. The same
approach has also been applied by Berg et al. (2006), Sonesson and
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