Pakistan Journal of Biological Sciences1028-88801812-5735Asian Network for Scientific Information10.3923/pjbs.2006.2173.2176Shams-EsfanabadiN. ShiraziA. 112006911Early embryonic mortality, indicated by cows returning to estrus before 24 day after insemination, and late embryonic mortality with cows returning to estrus after 24 days post insemination, contributes to repeat-breeding in dairy cows. The objective of this study was to evaluation the effect of post-insemination supplementation with CIDR (controlled internal drug release) for 14 days on pregnancy rate in repeat-breeders dairy cows. On day 5 after insemination, treated cows (n = 60) received a CIDR, which was removed on Day 19. Control cows (n = 54) did not receive any treatment. The study population was stratified by parity, days in milk and yield of milk production. Pregnancy rate between CIDR treated and control cows were 46.6 and 37%, respectively. There was no significant differences between two groups p<0.05.]]>Ahmad, N., S.W. Beam, W.R. Bulter, D.R. Deaver and R.T. Duby et al.,19967419431952Ayalon, N.,197854483493Ball, P.J.H.,199765167175Barr, H.L.,197558246247Bartolome, J.A., P. Melendez, D. Kelbert, K. Swift and J. Mc Hale et al.,20056310261037Ford, S.P.,198523145159Hanlon, D.W., P.J. Davidson, A.R. Hittmann and A.K. Joe,200563239245Hanlon, D.W., G.M. Jarratt, A.J. Millar and V.L. Douglas,20056319381945Lamming, G.E., A.O. Darwash and H.L. Back,198937245252Larson, S.F., W.R. Butler and W.B. Currie,19978012881295Linares, T.,19814189198Lopez-Gatius, F., P. Santolaria, J.L. Yaniz and R.H.F. Hunter,20046215291532Macmillan, K.L., V.K. Taufa, A.M. Day and A.J. Peterson,199143304304Macmillan, K.L. and A.J. Peterson,199333125Mann, G.E., G.E. Lamming, R.S. Robinson and D.C. Wathes,199934269274Pursley, J.R., R.W. Silcox and M.C. Wittbank,19988121392144Rensis, F.,19992α analog.]]>52259269Robinson, N.A., K.E. Leslie and J.S. Walton,198972202207Shelton, K., M.F. Gayerie De Abreu, M.G. Hunter, T.J. Parkinson and G.E. Lamming,199090110Spencer, T.E. and F.W. Bazer,2002718791898Starbuck, M.J., A. Robert and E. Keith Inskeep,2004842739Strong, A.J.H., J.M. Sreenan, M.G. Diskin, J.F. Mee, D.A. Kenny and D.G. Morris,20056412121224Van Cleef, J., M. Drost and W.W. Thatcher,199136795807Vanroose, G., A. de Kuif and A. Van Soon,200060131143Villarroel, A., A. Martino, R.H. Bondurant, F. Deletang and W.M. Sischo,20046115131520Wiltbank, J., H. Hawk, H. Kidder, W.G. Black, L.C. Ulberg and L.E. Casida,195539456461