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

Introduction
In Germany, the Piétrain pig is bred by independent herdbook breeding organizations
in which small numbers of specialized breeders are organized. Since 1980, the
number of Piétrain herdbook sows in Schleswig-Holstein (SH) decreased from 1,160
to 446 in 2009 (LWK SH, 2010). Such a small population is at risk because an
increase of inbreeding is expected with detrimental effects, such as inbreeding
depression, occurrence of genetic defects and loss of usable genetic variability for
genetic improvement (Falconer and Mackay, 1996). Gonzalez Lopez et al. (2011)
reported a continuously decreasing effective population size that resulted from
increasing inbreeding rates. In view of these developments a common breeding
evaluation system was implemented for the Piétrain populations in SH and Baden-
Württemberg (BW) in 2009 and boars from BW with comparable estimated breeding
values (EBV) are now also available to the herdbook breeders in SH. The Piétrain
herdbook organization in Schleswig-Holstein (SHZ) has expressed interest in an
application of dynamic optimization tool to allow the management of inbreeding with
additional potential for increasing genetic gain. In practice, selective breeding
programs may be considered as a two stage process. In the first instance, animals
are selected according to specific criteria and used as parents, a process that also
determines the genetic contribution of each parent to the next generation. In this
context, several authors have suggested different dynamic tools to maximize genetic
progress of selected animals while constraining the inbreeding rate at a predefined
value (Meuwissen, 1997; Grundy et al., 1998; Meuwissen und Sonesson, 1998;
Grundy, 2000). These methods optimize the number of selected animals and their
contributions to the next generation. Simulation studies showed that such
approaches could generate genetic gains more than 20% higher compared to
traditional selection based on BLUP EBV at the same rate of inbreeding (Meuwissen,
1997). After selecting parents for the next generation, the following step is to
establish a proper mating policy. Several mating systems, such as minimum
coancestry, compensatory and minimum variance mating, generate less inbreeding
while producing at least as much genetic gain as random mating in breeding
schemes where the parents are truncation selected (Caballero et al., 1996). The
mating system that is generally recommended is minimum coancestry mating
(Caballero et al., 1996; Sonesson and Meuwissen 2000; Meuwissen 2007).
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