Journal of Animal and Veterinary Advances 3 (8): 531·534, 2004 CD Grace Publications Network, 2004 The Synchronization of Ovulation and Estrus in Beef Cows That were Raised in Konya Animal Researh Intitue Using GnRH and PGF20 Faruk Aral, 'Mehmet Çolak and 'Seyit Ümütlü University of Harran, Faculty of Veterinary Medicine, Department of Reproduction and Artificial Insemination, Sanliurfa, Turkey 'Anirnal Researh lntitue, Konya, Turkey Abstract: The objective of the study was to compare the reproductive performance of beef cows synchronized for oestrus or ovulation using Prostaglandin F2 alpha (PGF 201 alone or with gonadotropin·releasing hormone (GnRHL. METHODS:Primiparous and multiparous beef cows (50 to 90 d postpartum; n;: 14) were assigned randomly to two treatment groups: 1) GnRH injection followed in 7 d by PGF20 injection then another GnRH injection 48 h later, and artificial insemination (AI) 24 h later the second GnRH injection (GnRH + PGF + GnRH group). 2) Injections of PGF20, 11 d apart, AI only after detected estrus following first and second PGF20 injections or when all remaining cows were timed artificial insemination (TA!) at 72 and 96 h (2 x PGF group). The Estrus detection rate (GnRH+PGF+GnRH group vs 2 x PGF group; 14.3 vs 28.6 %; P>0.1L. conception rate first insemination IGnRH + PGF+ GnRH group vs 2 x PGF group; 85.7 vs 71.4 %; P> O. 1) and pregnancy rate (GnRH + PGF + GnRH group vs 2 x PGF group; 71.4 vs 42.9;P> 0.1) were not different between the two groups. The ovulatıon synchronization did not decrease the fertility of beel cows when compared with the estrus synchronızation. Key words: Beef cows, estrus, ovulation, synchronization, PGF20 , GnRH Introduction Animal Research Institute in Konya, Turkey imported 25 purebred Charolais cows directly from France in 1992. These cows were raised from 20 head in 1992 to 25 head in 1999.The number of cows did not increase because of low fertility. Estrous detection failure is a primary problem that affects fertility in these cows. Recently, GnRH, together with PGF20 have been used to synchronize ovulation in beef cows (Lucv et al., 1986; Twagiramungu et al., 1995; Stevenson et al., 1997; Geary et al., 1998). Ovulation can be synchronize in beef and dairy cows by two injections of GnRH at a 9 days interval, with PGF20 injection on d 7. Cows then can receive a timed AI between 8 to 24 hours after the last GnRH injection without estrus behavior (Lueyet al., 1986; Pursley et al., 1997a; Geary et al., 1998; Lamb et al., 2001). Studies (Geary et al., 1998; Geary et al., 2001) have indicated that ovsynch protocol can improve fertility in beef cows. The use of PGF20 to synchronize estrus in beef cows contains various combinations of PGF2o .. When PGF20 is used as a luteolitic agent for estrus synchronization, cows must be in the luteal phase of the estrus cycle to respond to PGF20 (Burfening et sl., 1978, Diskin et al., 2002). Estrus is not exactly synchronized in the estrus synchronization program because follicular growth varies at the time luteal regression (Diskin et al, 2002). The objective of this study was to evaluate estrus detection, conception and pregnancy rate obtained by timed AI after synchronization of ovulation with GnRH·PGFo·GnRH compared with those after synchronization of estrus -. using two PGF20 , 11 dapart. Materials and Methods Animals: This study was carried out in charolais cows in animal research institute in Konya, Turkey. In this experiment, 14 Charolais cows (50 to 90 postpartum). 2 to 7 years old, were assigned by calving date and age (2·yr·old, 3·yr·old, and mature cows) to receive one of two treatment groups. Trea"tments: One of the treatment groups received GnRH·PGFo ·GnRH (GnRH + PGF + GnRH group) and the other (2 X PGF group) received two PGFo. Cows treated GnRH + PGF + GnRH protocol were injected 100 19 of GnRH (Receptal; Intervet Vet Ylaç Ltd. pti., Istanbul, Turkey) intramuscularly (IM) seven days later, cows received 25 mg of PGF20 (Estrumate: Sanofi Doöu Ytaç. A.P, Ystanbul, Turkey). Two days later, cows received a second injection of 100 19 GnRH and timed AI 24 h later. This group of cows were observed for estrus 3 d after PGF20 injection. The second group (2 X PGF group) was given 2 doses of PGF20, 11 dav apart, observed twice daily for esrrus. and inseminated 12 and 16 h after first detection of standing estrus. Cows that did not show estrus after the second injection of PGF20 received two tixed-tirne AI at 72 and 96 h after PGF20. The 2 X PGF group cows detected in estrus after two PGF20 injection received AI according to the a.rn-p.rn rule. 531