SELECTION EXPERIMENT IN PIGS TO IMPROVE C ARCASS TRAITS BY USING BIOCHEMICAL TRAITS OR ULTRASONIC MEASUREMENTS - 1ST COMMUNICATION - EXPERIMENTAL-DESIGN, DIRECT AND INDIRECT SELECTION RESPONSE

A selection experiment with German Landrace pigs was started in 1974 i n the experimental station Unterer Lindenhof of the Hohenheim Universi ty. 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 enz yme, glucose-6-P-dehydrogenase, 6-phosphocluconate-dehydrogenase, and NADP isocitrate-dehydrogenase. Measurements were made in tissue sample s 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 ultrason ic measurements at 85 kg of weight. A control line (K-0) without selec tion 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 fema les in each line were fattened and dissected for recording carcass tra its (second communication). The results can be summarized as follows: - Selection for enzyme activity in both directions was successful in t he selection differentials. In both selection lines (E(-), E(+)) the c umulative selection differentials were nearly equal. - In enzyme activ ity the expected development took place only in the E(-)-line. In the E(+)-line enzyme activity arised only in the first generations, the re duction after the fifth generation was unexpected. - In the divergent selection lines there was a progressive differentiation in the correla ted trait backfat thickness. The correlated selection response was in the expected direction. - The U--line, selected for low backfat thickn ess, shows also a clear reduction in backfat thickness.