In the current study, a meta-analysis was carried out by merging
outcomes resulting from 26 published studies in various breeds of sheep to
assess the influence of the FecB gene on litter size by applying the additive,
recessive, dominant, and co-dominant genetic models. The model with random
effects was used for data analysis according to the Cochran Q test and I2 quantity
statistical measures. Standardized mean difference (SMD) was applied to
measure the size effects of '+' and B alleles of FecB on the litter size. The
significant effect (P<0.01) of FecB genotypes on the litter size was identified
under the additive (SMD = 0.511), dominant (SMD = 0.469) and recessive (SMD
= 0.255) models. An increase in the litter size by approximately 0.47 lambs
(Dominant model) was associated with the first copy of the FecB gene and 0.25
lambs (Recessive model) with the second copy of FecB. The findings of the
current study supported the idea that BMPR1B would fundamentally influence the
litter size in sheep. Subsequently, it may be utilized in marker-assisted selection
programs to improve the genetic merit of litter size in the future. Introgression this
gene through crossbreeding programs in low prolific breeds may improve
reproductive performance.