Abstract
The report is presented on the construction of selection index for use in the selection of young boars and guts at around 90kgs. of live body weight in this experiment.
The selection index was to make use of such informations as daily gain of weight (X1) and thickness of backfat (X2), both measured on the animals subject to the selection, and the average area of eye muscle (X3) and average percent ham (X4) of the carcasses of littermate (full-brother) hogs.
Two selection indice were constructed in order to take care of the both cases where the young boar or gilt had two littermate hogs and where it had only one.
As for the genetic parameters necessary for construction of selection index, reliable estimates thereof neither for these particular experimental herds nor for any other Landrace herds in this country were available in time for the start of experiment, and the values assumed on the basis of the analysis of the performance test data for Middle Yorkshires accumulated for several years were used.
The selection indice constructed follow:
I2=0.0127X1-4.008X2+0.187X3+0.358X4 for the case of two littermate hogs, and I1=0.0129 X1-4.077X2+0.116X3+0.209X4+C for the case of only one littermate hog, where
C=(0.0127-0.0129)X1-(4.008-4.077)X2+(0.187-0.116)X3+(0.358-0.209)X4, X1-X4 denoting the herd averages for the respective traits.
These selection indice, as mentioned in the preceeding report, were to be in use for two generations from the start of the experiment, and then to be revised, with new estimates of parameters and from a new methodological viewpoint, for application from the third generation on.
