1. College of Animal Science and Technology; Shaanxi Key Laboratory of Molecular Biology for Agriculture; Northwest A&F University; Yangling Shaanxi 712100 China
2. Animal Genomics & Improvement Laboratory; USDA-ARS; BARC-East Beltsville MD 20705 USA
3. Institute of Cellular and Molecular Biology; Jiangsu Normal University; Xuzhou Jiangsu 221116 China
4. Department of Animal Science; Macdonald Campus; McGill University; 21111 Lakeshore Ste Anne de Bellevue QC H9X 3V9 Canada