Acta Veterinaria Scandinavica 2009, 51:48 http://www.actavetscand.com/content/51/1/48 Ovsynch may be the first synchronisation protocol that has performed well in lactating dairy cows but not in heif- ers. Although the number of heifers involved in the present study was low, and thus, significant results were not reached, it seemed that proportionally more heifers were rejected from the program due to unresponsiveness; the conception rate was 7.7 percentage points lower than the overall average. Conclusion The use of fixed-time AI after the Ovsynch protocol in beef herds seems to give acceptable pregnancy results, and its effect on the saving of labour is notable. However, final profitability depends much on the herd and the objectives involved. Season and suckling during the insemination period did not seem to affect fertility. Interval from calv- ing to start of the protocol had a clear influence: the fertil- ity was the best in the group having the shortest interval, 50-70 days. The effect of parity was not clear, but it seemed that this protocol does not lend for heifers as well as for cows. Competing interests The author declares that he has no competing interests. Acknowledgements The author wishes to thank Mr. Gunnar Backman and Ms. Heli Äyräväinen for their kind co-operation during this experiment. References 1. Geary TW, Whittier JC, Downing ER, LeFever DG, Silcox RW, Hol- land MD, Nett TM, Niswender GD: Pregnancy rates of postpar- tum beef cows that were synchronized using Syncro-Mate-B or the Ovsynch protocol. J Anim Sci 1998, 76:1523-1527. 2. Louis TM, Hafs HD, Seguin BE: Progesterone, LH, estrus and ovulation after prostaglandin F2 alpha in heifers. Proc. Society for Experimental Biology and Medicine 1973, 143:152-155. 3. Oxender WD, Noden PA, Louis TM, Hafs HD: A review of pros- taglandin F2 alpha for ovulation control in cows and mares. Am J Vet Res 1974, 35:997-1001. 4. Lauderdale JW, Seguin BE, Stellflug JN, Chenault JR, Thatcher WW, Vincent CK, Loyancano AF: Fertility of cattle following PGF2 alpha injection. J Anim Sci 1974, 38:964-967. 5. Hafs HD, Manns JG, Drew B: Onset of oestrus and fertility of dairy heifers and suckled beef cows treated with prostaglan- din F2 alpha. Anim Prod 1975, 21:13-20. 6. Stellflug JN, Louis TM, Hafs HD, Seguin BE: Luteolysis, estrus and ovulation, and blood prostaglandin F after intramuscular administration of 15, 30 or 60 mg prostaglandin F2 alpha. Prostaglandins 1975, 9:609-615. 7. Lucy MC, Stevenson JS, Call EP: Controlling first service and calv- ing interval by prostaglandin F2 alpha, gonadotropin-releas- ing hormone, and timed insemination. J Dairy Sci 1986, 69:2186-2194. 8. Stevenson JS, Lucy MC, Call EP: Failure of timed inseminations and associated luteal function in dairy cattle after two injec- tions of prostaglandin F2-alpha. Theriogenology 1987, 28:937-946. 9. Larson LL, Ball PJH: Regulation of estrous cycles in dairy cattle: a review. Theriogenology 1992, 38:255-267. 10. Pursley JR, Mee MO, Wiltbank MC: Synchronization of ovulation in dairy cows using PGF2 alpha and GnRH. Theriogenology 1995, 44:915-923. 11. Pursley JR, Kosorok MR, Wiltbank MC: Reproductive manage- ment of lactating dairy cows using synchronization of ovula- tion. J Dairy Sci 1997, 80:301-306. 12. Pursley JR, Wiltbank MC, Stevenson JS, Ottobre JS, Garverick HA, Anderson LL: Pregnancy rates per artificial insemination for cows and heifers inseminated at a synchronized ovulation or synchronized estrus. J Dairy Sci 1997, 80:295-300. 13. Pursley JR, Silcox RW, Wiltbank MC: Effect of time of artificial insemination on pregnancy rates, calving rates, pregnancy loss, and gender ratio after synchronization of ovulation in lactating dairy cows. J Dairy Sci 1998, 81:2139-2144. 14. Moreira F, de la Sota RL, Diaz T, Thatcher WW: Effect of day of the estrous cycle at the initiation of a timed artificial insem- ination protocol on reproductive responses in dairy heifers. J Anim Sci 2000, 78:1568-1576. 15. Vasconcelos JLM, Silcox RW, Rosa GJM, Pursley JR, Wiltbank MC: Synchronization rate, size of the ovulatory follicle, and preg- nancy rate after synchronization of ovulation beginning on different days of the estrous cycle in lactating dairy cows. Theriogenology 1999, 52:1067-1078. 16. Heinonen K: Relationship between rectal findings of corpus luteum and whole milk progesterone levels in postpartum dairy cows. Acta Vet Scand 1988, 29:239-243. 17. Gümen A, Guenther JN, Wiltbank MC: Follicular size and response to Ovsynch versus detection of estrus in anovular and ovular lactating dairy cows. J Dairy Sci 2003, 86:3184-3194. 18. Burke JM, de la Sota RL, Risco CA, Staples CR, Schmitt EJP, Thatcher WW: Evaluation of timed insemination using a gonadotro- pin-releasing hormone agonist in lactating dairy cows. J Dairy Sci 1996, 79:1385-1393. 19. Peters MW, Pursley JR: Timing of final GnRH of the Ovsynch protocol affects ovulatory follicle size, subsequent luteal function, and fertility in dairy cows. Theriogenology 2003, 60:1197-1204. 20. Stevenson JS, Kobayashi Y, Shipka MP, Rauchholz KC: Altering con- ception of dairy cattle by gonadotropin-releasing hormone preceding luteolysis induced by prostaglandin F2 alpha. J Dairy Sci 1996, 79:402-410. 21. Geary TW, Whittier JC, Hallford DM, MacNeil MD: Calf removal improves conception rates to the Ovsynch and CO-Synch protocols. J Anim Sci 2001, 79:2536-2541. 22. Lamb GC, Stevenson JS, Kesler DJ, Garverick HA, Brown DR, Salfen BE: Inclusion of an intravaginal progesterone insert plus GnRH and prostaglandin F2 alpha for ovulation control in postpartum suckled beef cows. J Anim Sci 2001, 79:2253-2259. 23. Kawate N, Itami T, Choushi T, Saitoh T, Wada T, Matsuoka K, Uenaka K, Tanaka N, Yamanaka A, Sakase M, Tamada H, Inaba T, Sawada T: Improved conception in timed-artificial insemination using a progesterone-releasing intravaginal device and Ovsynch protocol in postpartum suckled Japanese Black beef cows. Theriogenology 2004, 61:399-406. 24. Sterry RA, Jardon PW, Fricke PM: Effect of timing of Cosynch on fertility of lactating Holstein cows after first postpartum and Resynch timed-AI services. Theriogenology 2007, 67:1211-1216. 25. Moreira F, Orlandi C, Risco CA, Mattos R, Lopes F, Thatcher WW: Effects of presynchronization and bovine somatotropin on pregnancy rates to a timed artificial insemination protocol in lactating dairy cows. J Dairy Sci 2001, 84:1646-1659. 26. El-Zarkouny SZ, Cartmill JA, Hensley BA, Stevenson JS: Pregnancy in dairy cows after synchronized ovulation regimens with or without presynchronization and progesterone. J Dairy Sci 2004, 87:1024-1037. 27. Small JA, Colazo MG, Kastelic JP, Mapletoft RJ: Effects of proges- terone presynchronization and eCG on pregnancy rates to GnRH-based, timed-AI in beef cattle. Theriogenology 2009, 71:698-706. 28. Lotthammer K-H: Umweltbedingte Fruchtbarkeitsstörungen. In Fertilitätsstörungen beim weiblichen Rind Edited by: Grunert E, Berch- told M. Berlin and Hamburg: Verlag Paul Parey; 1982:390-432. 29. Rautala H: Fertility in Finnish dairy cattle. Impact on milk pro- duction, variation according to cow and environmental fac- tors and characterization of fertility problem cows. In PhD thesis College of Veterinary Medicine; Helsinki; 1991. 30. Butler WR, Smith RD: Interrelationship between energy bal- ance and postpartum reproductive function in dairy cattle. J Dairy Sci 1989, 72:767-783. Page 5 of 6 (page number not for citation purposes)