| heal.abstract |
A selection experiment with German Landrace pigs was started in 1974 in the experimental station Unterer Lindenhof of the Hohenheim University. Four selection lines were established from a basic population. In divergent directions the lines E(-) and E(+) were selected for the sum of the specific activities of the NADPH-generating enzymes: malic enzyme, glucose-6-P-dehydrogenase, 6-phosphocluconate-dehydrogenase, and NADP isocitrate-dehydrogenase. Measurements were made in tissue samples from backfat, taken by biopsy at an age of 90 and 120 days. A third line (U-) was selected for low backfat thickness, measured by ultrasonic measurements at 85 kg of weight. A control line (K-0) without selection was included. In each generation and each selection line about 80 male and 40 female pigs were tested in single boxes. These pigs were produced from 8 boars and 16 sows, in the control line K-0 the number of parents were about 16 boars and 32 sows. The selection period was 9 generations. After the last generation 76 castrated males and 75 females in each line were fattened and dissected for recording carcass traits (second communication). The results can be summarized as follows: - Selection for enzyme activity in both directions was successful in the selection differentials. In both selection lines (E(-), E(+)) the cumulative selection differentials were nearly equal. - In enzyme activity the expected development took place only in the E(-)-line. In the E(+)-line enzyme activity arised only in the first generations, the reduction after the fifth generation was unexpected. - In the divergent selection lines there was a progressive differentiation in the correlated trait backfat thickness. The correlated selection response was in the expected direction. - The U--line, selected for low backfat thickness, shows also a clear reduction in backfat thickness. |
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