[Li, Zhen; Wang, Junjun; Lin, Gang; Dai, Zhaolai; Lai, Changhua; Wu, Guoyao; Liu, Chuang] China Agr Univ, State Key Lab Anim Nutr, Beijing 100094, Peoples R China.
[Feng, Cuiping] China Japan Friendship Hosp, Dept Obstet & Gynecol, Beijing, Peoples R China.
[Li, Zhen] China Agr Univ, State Key Lab Plant Physiol & Biochem, Beijing 100094, Peoples R China.
[Fan, Zhiyong] Hunan Agr Univ, Coll Anim Sci & Technol, Changsha, Hunan, Peoples R China.
[Wu, Guoyao] Texas A&M Univ, Dept Anim Sci, College Stn, TX 77843 USA.