Mutations in the FecL locus are associated with large variation in ovulation rate and litter size in the French Lacaune sheep breed. It has been shown that the B4GALNT2 gene within the FecL locus is most likely responsible for the high fecundity in the French breed. In this study, we have highlighted the segregation of the FecLL mutation within the B4GALNT2 gene in North African sheep breeds and notably in the highly prolific D'man breed. Genotyping of a sample of 183 Tunisian D'man individuals revealed a high frequency (0.65) of the prolific allele FecLLwhich was attributed to the adoption of a decades‐old breeding strategy based on the selection of ewe lambs born from large litter size. Homozygous LL ewes showed a significantly increased litter size compared to heterozygous and non‐carrier ewes (FecLL/FecLL = 2.47 ± 0.09 vs. FecLL/FecL+ = 2.23 ± 0.09, p < 0.05 and FecL+/FecL+ = 1.93 ± 0.18, p < 0.01). The presence of the FecLLpolymorphism in both D'man and Lacaune breeds argues for an ancestral origin of this mutation and brings an answer to the old question of the genetic determinism of the extreme prolificacy of the D'man ewes. The results of this study can help to establish planned genotype‐based mating allowing both higher profit for the breeders and an optimal management of the FecLL mutation in D'man sheep populations.