“…Among these candidate genes, the GDF9 (growth and differentiation factor 9) gene which belongs to transforming growth factor β superfamily (TGFβ) and mapped on ECA14 plays crucial roles in determining follicle growth and controlling the ovulation rate (Hanrahan et al, ; Paulini & Melo, ). In addition, several studies have confirmed the involvement of genetic variants of GDF9 in women with dizygotic twins (Montgomery et al, ; Palmer et al, ) and with litter size in domesticated animals including sheep (El Fiky, Hassan, & Nassar, ; Hanrahan et al, ; Nicol et al, ), pig (Zhang, Du, Chen, Yang, & Zhang, ), goat (Chu et al, ; Feng et al, ) and cattle (Tang, Yang, Li, & Yang, ).…”