Genetic and phenotypic trends in Polish large white nucleus swine herds.

Performance test records collected from 1978 to 1987 from on-farm tests of young Polish Large White boars from 94 herds and reproductive records of Polish Large White sows from 81 nucleus farms were used to estimate the phenotypic, environmental, and genetic trends. There were, after editing, 114,347 boar performance records and 41,080 litter records on sows. Both data sets were analyzed by use of an animal model. Estimated annual phenotypic and environmental trends were relatively large and desirable and were, respectively, .17 +/- .05, .11 +/- .05 (number born alive); .16 +/- .04, .10 +/- .04 (21-d litter size); 1.86 +/- .63, 1.43 +/- .62 (21-d litter weight, kg); 6.80 +/- .60, 6.76 +/- .72 (average daily gain, g/d); -.065 +/- .007, -.058 +/- .023 (backfat thickness, mm); -2.76 +/- .28, -2.75 +/- .29 (days to 110 kg). In contrast, all estimated genetic trends were relatively small and not always favorable. The genetic trends estimated from animal, sire and dam genetic values were, respectively, .01 +/- .01, .02 +/- .01, .01 +/- .01 (number born alive and 21-d litter size); .04 +/- .06, .10 +/- .05, .05 +/- .04 (21-d litter weight, kg); .04 +/- .04, .50 +/- .10, -.43 +/- .05 (average daily gain, g/d), -.009 +/- .001, -.015 +/- .002, -.004 +/- .0004 (backfat thickness, mm); and -.01 +/- .01, -.17 +/- .04, .19 +/- .02 (days to 110 kg). Neither examination of selection practices nor boar utilization provided an explanation for the lack of genetic progress.