Estimation of realised genetic trends in French Large White pigs from 1977 to 1998 for production and meat and fat quality traits using frozen semen

An experimental design has been implemented in INRA’s experimental herds in order to estimate realised genetic trends from 1977 to 1998 in the French Large White (LW) pig breed. LW sows were inseminated with stored frozen semen of 17 LW boars born in 1977 or with semen of 23 LW boars born in 1998, producing 30 litters for each group of sires.Within each experimental group, 15 males and 80 females were randomly chosen and mated to produce a second generation of animals that were fattened and slaughtered to compare their performances for growth, carcass and quality traits. The results, obtained on about 2000 females and castrates, showed that selection resulted in a highly significant decrease of all carcass adiposity indicators (e.g. -5.2 ± 0.7 mm in 21 years for average backfat thickness measured on 20-week-old animals) and in a strong increase of carcass lean content. The average daily gain during the commercial fattening period improved moderately (77 ± 27 g/d in 21 years). A negative trend was found for ultimate pH (uPH) measured on several ham and loin muscles (from –0.10 ± 0.06 for uPH of Gluteus superficialis muscle up to –0.16 ± 0.07 for uPH of Semimembranosus muscle in 21 years). Reflectance of Gluteus medius muscle tended to increase, but the water holding capacity of Gluteus superficialis muscle significantly improved. The water content and the proportion of polyunsaturated fatty acids of backfat tissue showed unfavourable trends. Finally, the intramuscular lipid content of Longissimus dorsi muscle remained unchanged (2.45%).