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Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học thế giới đề tài: Estimation of genetic variability and selection response for clutch length in dwarf brown-egg layers carrying or not the naked neck gene | 219 Genet Sei. Evol. 35 2003 219-238 INRA EDP Sciences 2003 DOI 10.1051 gse 2003005 Original article Estimation of genetic variabilitY and selection response for clutch length in dwarf brown-egg laYers carrYing or not the naked neck gene Chih-Feng Chena b Michele Tixier-Boicharda a Laboratoire de génétique factorielle Departement de génétique animale Institut national de la recherche agronomique 78352 Jouy-en-Josas Cedex France b Department of Animal Science National Chung-Hsing University Taichung Taiwan Received 13 May 2002 accepted 12 August 2002 Abstract - In order to investigate the possibility of using the dwarf gene for egg production two dwarf brown-egg laying lines were selected for 16 generations on average clutch length one line LI was normally feathered and the other L2 was homozygous for the naked neck gene na. a control line from the same base population dwarf and segregating for the na gene was maintained during the selection experiment under random mating. The average clutch length was normalized using a Box-Cox transformation. Genetic variability and selection response were estimated either with the mixed model methodology or with the classical methods for calculating genetic gain as the deviation from the control line and the realized heritability as the ratio of the selection response on cumulative selection differentials. Heritability of average clutch length was estimated to be 0.42 0.02 with a multiple trait animal model whereas the estimates of the realized heritability were lower being 0.28 and 0.22 in lines LI and L2 respectively. REML estimates of heritability were found to decline with generations of selection suggesting a departure from the infinitesimal model either because a limited number of genes was involved or their frequencies were changed. The yearly genetic gains in average clutch length after normalization were estimated to be 0.37 0.02 and 0.33 0.04 with the classical methods 0.46 0.02 and 0.43 0.01 with animal model .
