Qingqing Liu, Zhilong Tian, Chunhuan Ren, Zijun Zhang and Mingxing Chu, 2025. Polymorphisms of ESR1, PGR and CYP19A1 Genes and their Association with Litter Size in Small-Tailed Han Sheep. Pakistan J. Zool., 57: 539-548. DOI: https://dx.doi.org/10.17582/journal.pjz/20220118110134