TAILIEUCHUNG - Báo cáo sinh học: " Expected efficiency of selection for growth in a French beef cattle breeding scheme. I. Multistage selection of bulls used in artificial insemination"

Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học Journal of Biology đề tài: Expected efficiency of selection for growth in a French beef cattle breeding scheme. I. Multistage selection of bulls used in artificial insemination | Genet Sei Evol 1995 27 149-170 Elsevier INRA 149 Original article Expected efficiency of selection for growth in a French beef cattle breeding scheme. I. Multistage selection of bulls used in artificial insemination F Phocas JJ Colleau F Ménissier Institut national de la recherche agronomique station de génétique quantitative et appliquée 78352 Jouy-en-Josas cedex France Received 24 February 1994 accepted 18 October 1994 Summary - Genetic improvement of beef cattle for growth traits implies selection on both direct and maternal effects through on-farm and station individual and progeny performance tests. To optimize the use of these tools a French selection scheme of artificial insemination Al bulls is modelled including its main components ie 2 kinds of station performance tests and 2 kinds of progeny tests farm and station . Three breeding objectives are derived in order to represent the heterogeneity of production systems Hs for suckler herds Hi for suckler-fattening herds and an average objective Hg considered as the most realistic for the whole breed. These objectives include direct and maternal genetic effects on weaning weight and direct effects on final weight. Economic demographic and genetic parameters are derived for the Limousin breed. Multistage selection procedures are algebraically optimized by finding selection thresholds which maximize response for the breeding objectives. The current scheme appears to be more efficient for Hi than for Hs. However whatever the objective maternal genetic response is expected to be slightly negative due to a negative correlation between direct and maternal genetic effects. Standard deviations of genetic responses are calculated to take into account some uncertainty on estimates of genetic parameters. With a 95 confidence interval maternal genetic response could be positive. An alternative to this complex scheme is considered using only one kind of station performance test and the on-farm progeny test. The increase of

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