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

decades. Accordingly, all populations had common boars with progeny. This resulted
in an average genetic similarity of 11.17%. The average genetic relationship
coefficients between the five breeding organizations confirmed that the populations
are genetically linked and ranged between 2.57 % and 4.52 %. Additionally, in all
populations, at least one of the five ancestors with the largest marginal contributions
to the reference population originated from another herdbook population. One of the
most important ancestors was common for three populations. Over the past 30 years,
the contribution of foreign founders to the populations has increased as a
consequence of exchange of genetic material. The various measures of
connectedness indicated that there are sufficient genetic links between the five
herdbook populations to enable an overall breeding value estimation system.
In chapter three, the properties and consequences through the application of a
concept to maintain genetic variability while maximizing genetic gain in the Piétrain
herdbook population in Schleswig-Holstein were investigated. Especially the
additional benefit by considering boars from Piétrain herdbook population in Baden-
Württemberg in selection decisions was of particular interest. A two-step selection
and mating strategy was applied. At first, animals were selected with the optimum
contribution selection method to identify elite sows and boars. The optimum
contribution selection theory using official estimated breeding values was applied for
different constraints on relationship. The number of sows was fixed at a constant
value of 50. In general, the optimal number of boars decreased rapidly as the
relationship constraint was relaxed. The lowest achievable level of relationship in the
next generation wase 2.7% for SH boars and only 1.9% when BW boars were
included. Furthermore, a higher average breeding value of selected animals could be
achieved by including BW boars. Consequently, it is recommended to consider BW
boars in selection of elite boars. Contributions from selected boars and sows were
used to develop specific mating plans by applying minimum coancestry mating with a
linear programming technique. Minimum coancestry mating reduced average
coancestry by at least 64%. This two-step selection and mating strategy requires less
computer time, compared to a one step mating scheme, where all selection
candidates are included in the mating step. Application of optimum contribution
selection combined with minimum coancestry mating seems to be a promising tool to
select elite animals and to control inbreeding while maintaining genetic progress
under practical conditions.
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