نبذة مختصرة : National audience ; The selection of French dairy sheep breeds is presently based on annual progeny-testing of 440, 50, 30 30, and 150 AI rams, respectively in Lacaune (LL), Basco-Bearnaise (BB), Corse, black-faced Manech (BFM), and redfaced Manech (RFM) breeds. Since 2010 we have been studying the feasibility of genomic selection (GS) in the above breeds. The main results are the following: (1) the size of the reference populations reached in 2013 4841 (LL), 509 (BB), 331 (BFM), 1424 (RFM) AI rams; (2) since the accuracies of different genomic evaluation methods were shown to be similar, the single step GBLUP method was chosen; (3) a gain in accuracy of genomic predictions over parent average ranged from 0.10 to 0.20, depending on the trait and breed; (4) a gain in accuracy was more limited than in large breeds like dairy cattle, in agreement with a larger effective population size in French dairy sheep breeds. The design of a genomic breeding scheme in dairy sheep is comparable to hybrid schemes implemented in small Scandinavian dairy cattle populations, which combine an initial genomic selection with a moderate phenotype selection at the arrival of the first proofs. With a genomic selection pressure between 1/3 and ¼ in 3 month-old rams, the annual genetic gain will be increased by 10 to 15 % with a reduction of the AI livestock in the range of 20-40 %, hardly balancing genotyping costs. A genomic experiment carried out in AI LL rams born in 2011 and 2012 validated such a GS pressure around 1/3. Finally, the breeding organizations decided to move towards genomic selection in 2015 in Lacaune and in a near future in Pyrenean breeds, expecting a greater flexibility from the genomic scheme. SG therefore leads to major changes in terms of selection of dairy sheep in France with upcoming changes in technical, economic and organizational aspects. ; La sélection des brebis laitières en France est fondée actuellement sur le testage sur descendance de 440, 50, 30, 30 et 150 béliers d’IA par an, respectivement en races ...
No Comments.