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

Holstein. The data record included a total of 23,201 animals born from 1980 to 2009
with sire and dam identification number, sex, herdbook organization and year of birth.
Selection of elite animals
Two selection steps were used to select elite parents for the next generation. The
first, included performance and additive breeding values requirements set by the
breeding organization. The second was the optimum contribution selection method,
implemented in the program GENCONT (Meuwissen, 2002), to select males and
females with their optimal mating frequencies to breed the next generation.
1) Performance and breeding values requirements
At first, potential elite animals were selected following stringent assessment of
performance. Minimum requirements were determined by the representatives of
SHZ. The progeny of potential elite animals, tested in the performance test station of
SH, were required to have an average daily gain of >750 g, feed conversion ratio
59 cm², fat to lean ratio 6. Moreover, additive breeding values of growth
performance have to be positive. For a potential elite animal, the performance and
breeding values had to be within the predetermined thresholds for all traits. Table 1
and 2 give an overview of the performance of potential elite candidates.
2) Optimum contribution selection
In the second step, the optimum contribution selection method of Meuwissen (1997)
was used to obtain the number of individuals to be selected and the number of
offspring each of them should contribute to the next generation. The method implies
a maximization of the genetic level of the next generation
41
G
t+ 1
= c'
t
EBVt
, where
t
c is a
vector of genetic contributions of the selection candidates to generation t + 1 and
EBV
t
is a vector of estimated breeding values in generation t . The objective function
is maximised for c
t
under two restrictions. First, the rates of inbreeding are restrained
to a preset level by constraining the average coancestry between selected animals to
C t+ 1 = c'
t
At
c / 2, where A t
t
is the relationship matrix between selection candidates,
t
C t+ 1 = 1−
(1 − ∆F d
) and ∆ Fd
is the desired rate of inbreeding. The second restriction is
on the sum of the contributions of male and female to 1 / 2, respectively, with
Q ' c t
= (1/ 2) , where Q is an n × 2 incidence matrix of the sex of the selection