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Mass Selection in a Pig Population: Correlated Changes in Carcass Merit

University of Alberta, Edmonton, Alberta, Canada T6H 2H1

Abstract

Correlated responses in carcass traits are described for a selection experiment involving a control population (C) and three selection lines defined as maximum growth (G), minimum backfat (B) and a phenotypic index line (I) combining increased growth and reduced backfat. Less backfat (P<.01) and greater predicted lean content (P<.05) relative to the contemporary control characterized the three selection lines in generation 9. The largest changes in these traits were recorded by the B and I lines, both deviating from the control (P<.01) by 5% in predicted lean content of the carcass and by –21 to –25% in backfat. These changes in the B and 1 lines were accompanied by modest increases (P<.05) in the proportion of ham (> 2.0%) and longissimus muscle area (> 3%) and by a substantial increase (P<.01) in the proportion of lean in the ham face (> 11%). Carcass length changed significantly in the G line (–.9%) and the B line (1.6%) but not in the I line (.5%). Meat quality attributes, measured for the C and I populations at generation 12, showed no adverse relationships with lean content. Indeed the subjective color-structure score for the I line was marginally superior to the C population. At generation 12 the line averages for percent dissected lean of ham, loin and shoulder were 50.7 ± .7% (I) and 46.1 ± .7% (C). These results support the hypothesis that selection based on the phenotypic index resulted in substantial improvement of carcass lean content and growth rate without compromising lean quality.

¹ Research conducted by senior author at the Canada Agr. Res. Sta., Lacombe.

² Mailing address: Box 1810, Lacombe, Alberta, CanadaT0C 1S0.

³ Natl. Res. Coucil Post-Doctorate Fellow at Lacombe, 1975 to 1977. Present address: Natl. Inst. of Anim. Ind., Tsukuba Norindanchi, P. O. Box 5, Ibaraki 305, Japan.