tailieunhanh - báo cáo khoa học: "Estimated genetic trends for carcass traits in two French Michèle TIXIER"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: Estimated genetic trends for carcass traits in two French Michèle TIXIER | Génét. Sél. Evol. 1986 18 2 185-212 Estimated genetic trends for growth and carcass traits in two French pig breeds Michèle TIXIER and p. SELLIER . Station de Génétique quantitative et appliquée Centre de Recherches zootechniques F 78350 Jouy-en-Josas Summary Genetic trends for growth and carcass traits were estimated in the Large White LW and French Landrace FL pig breeds using the records of 7529 LW and 4118 FL gilts reared in progeny-test stations between 1970 and 1981 and 34887 LW and 16779 FL boars reared in performance-test stations between 1969 and 1981. Three methods of estimation were used. Method 1 was the within-sire regression of progeny s performance on time taking into account the selection of sires on sons records in the boar performance-test data set Sires and dams were grouped into cohorts according to year of birth and the cohort effects were estimated either by a fixed linear model method 2 or by a mixed linear model method 3 . Differences between sire and dam trends were seldom significant. Method 2 under-estimated the genetic gain when sires or dams were being selected on the records of their offspring on test. The results of methods 1 and 3 being pooled the estimated annual genetic trends were di LW and FL for average daily gain ADG g in the boar performance-test . data set LW and FL for ADG in the progeny-test . data set LW and FL for food conversion ratio FCR kg feed kg gain in the . data set LW and FL for FCR in the . data set LW and FL for average backfat thickness mm in the . data set LW and FL for percentage lean in the . data set. Carcass length increased as a correlated response to selection whereas meat quality traits did not deteriorate. The main feature of this study . the higher yearly response in carcass traits around 1 p. 100 of the mean than in growth traits around p. 100 of the