Three generations of selection for increased weight at 70 d of age was practiced in Landrace pigs. Performance records at 70 d were collected on 708 pigs from 47 sires and 105 dams. Each generation, nine boars and 27 gilts with heaviest 70 d weights were selected to produce the next generation of select line pigs. Random selection of one boar from each of the five foundation sire lines and a gilt from each litter was used to maintain the control line. Responses to selection were estimated by regression of generation means adjusted for environmental effects on generation number. Weight at 70 d increased 1.08 + .47 kg/generation which represented 10.4$ improvement. The realized heritability of 70 d weight was .27 ± .12. Selection for heavy weight at 70 d resulted in decreased leanness in the select line carcasses as indicated by the negative regression coefficients for loin eye area (-.58±.23 cm2) anci lean cuts percentage (-.35±.14$) and the positive regression coefficient for lOth-rib backfat thickness (.09±.02 cm).

S. B Jungst, D. L Kuhlers

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume XI. Genetics of reproduction, lactation, growth, adaptation, disease, and parasite resistance., , 425–430, 1986
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