3Pursley, J.R., et al. Synchronization of ovulation in dairy cows using PGF2alpha and GnRH[J].Theriogenology, 1995,44:915-923.
4Pursley,J.R.,Kosorok,M.R.,Wihbank,M.C.,Reproductive management of lactating dairy cows using synchronization of ovulation [J].J.Dairy Sci. 1997, (80) :301-306.
5Kyoji Yamada Development of Ovulation Synchronization and Fixed Time Artificial Insemination in Dairy Cow[J].J.Reprod. Dev.2005,51:177-186.
8Fricke P M. Scanning the future:Ultrasonography as a reproductive management tool for dairy cattle[J]. J Dairy Sci, 2002,85(8):1 918-1 926.
9Nyland T G, Mattoon J S. Veterinary diagnostic ultrasound[M]. Pennsylvania :W. B. Saunders Company, 1995. 305-320.
10Nation D P,Malmo J,Davis G M,et al. Accuracy of bovine pregnancy detection using transrectal ultrasonography at 28 to35 days after insemination[J]. Australian Vet J,2003,81(1-2):63-65.