Increasing Prolificacy of Awassi and Assaf Breeds by Introgression of the Fecb (booroola) Mutation: Achievements and Challenges

Awassi and Assaf are local Israeli sheep breeds with prolificacies of ~1.30 and ~1.65 lambs born/ewe lambing (LB/EL), respectively. Introgressing the B (Booroola) allele of the FecB locus into these breeds led to the formation of prolific strains designated 'Afec Awassi' and 'Afec Assaf', in which lamb production under both intensive and semi-intensive conditions is higher than in the respective local breeds by ~0.8 LB/EL and ~0.5 live lambs born/ewe lambing. Lower survival rate at birth in multifetal pregnancies reduces the ability to fully exploit the economic potential of the Afec strains. A genome-wide association study revealed QTLs on ovine chromosomes 1, 8, 10, 26 and X associated with lamb survival rate at birth as a maternal trait.