Suitability of microsatellites BM1329 and OarAE101 as markers for the introgression of the Fec(B) locus into different sheep breeds

Litter site in sheep can be improved by introgression of the Fec(B) gene. G enetic markers closely linked to the Fec(B) locus can be used to detect gen e carriers. The efficiency of introgression can be increased by using marke r assisted selection. Individuals of the prolife breeds Tyrolean Mountain s heep (n-41). Romanov (n=43), East Friesian Milksheep (n=35) and Merinoland sheep (n=265) were genotyped with the microsatellite markers OarAE101 and B M1329 linked to the Fec(B) gene to estimate allele frequencies of both micr osatellites in these breeds. The frequencies of the microsatellite alleles linked to the Fec(B) gene in Merinoiand sheep were 0.07 and 0.1 respectivel y. The alleles occurred also in the other breeds (Tyrolean Mountain sheep, Romanov and East Friesian Milksheep) but with mostly higher frequencies. Fu rthermore the segregation of the microsatellite alleles war studied in fami lies produced by mating Merinoland sheep ewes (Fec+/Fec+) with two heterozy gous Booroola Merino rams (Fec+/Fec(B)) in order to use these markers withi n an indirect gene test. The recombination rate between BM 1329 and OarAE10 1 was 13 cM (LOD score 14.6).