
TY  - JOUR
A1  - Ushijima, H. 
A1  - Tatsuno, N. 
A1  - Hara, Y. 
A1  - Mori, T. 
A1  - Murata, H. 
A1  - Ohno, M. 
T1  - 219 COMPARISON OF ESTRUS&#8211;OVULATION SYNCHRONIZATION TREATMENTS USING HOLSTEIN HEIFERS AS EMBRYO TRANSFER RECIPIENTS
JF  - Reproduction, Fertility and Development
JO  - Reprod. Fertil. Dev.
Y1  - 2006
VL  - 19
IS  - 1
SP  - 226
EP  - 227
KW  - 
UR  - https://doi.org/10.1071/RDV19N1AB219 
N2  - The Ovsynch system (Pursley et al. 1995 Theriogenology 44, 915&#8211;923) has been effectively employed as the synchronization method of recipients for embryo transfer (ET) (Nishisouzu et al. 2004 Reprod. Fertil. Dev. 16, 212&#8211;213). To establish the most effective Ovsynch system, we experimentally assessed 3 different protocols by comparing resultant estrus-synchronization rates of Holstein heifers and pregnancy rates of the recipients after ET. Holstein heifers averaging 14&#8211;15 months old and weighing over 330 kg were used in this study. They were randomly separated into the following 3 groups: (1) Select-synch (SS) group: an intramuscular (IM) injection of 50 µg GnRH analog was given to heifers at a random stage of the estrus cycle, followed 7 days later by 2 IM injections of 7.5 mg PG analog at an interval of 6 h; (2) Co-synch (CS) group: another IM injection of 50 µg GnRH was given to the SS group at 48 h after the first injection of PG; and (3) Heat-synch (HS) group: an IM injection of 0.75 mg estradiol benzoate was given to the SS group at 24 h after the first injection of PG. Estrus detection was evaluated twice daily by visual observation and use of a Heat Mount Detector. All heifers were additionally injected with 1500 IU hCG 5 days after estrus, to ensure favorable luteal function (Nishigai et al. 2001 J. Reprod. Dev. 47, 283&#8211;294). Rectal palpation was used to select acceptable recipients, i.e. those having functional corpora lutea (CL) e17 mm in diameter for 7 days after showing estrus (Nishisouzu et al. 2004 Reprod. Fertil. Dev. 16, 212&#8211;213). The size of CL e17 mm was determined by rectal palpation by skillful transferors. Fresh embryos collected from super-ovulated cattle 7 days after estrus were nonsurgically transferred only into acceptable recipients that had functional CL and were properly synchronized, 7&#8211;8 days after estrus. Final diagnosis of pregnancy was carried out 60 days after ET. Data were analyzed by the chi-square test. The HS group showed significantly higher (P < 0.01) rates of estrus synchronization (87/89: 98%) at 24&#8211;72 h after PG injection, estrus detection (98%), and acceptable suitability as recipients with a functional CL (92%) compared to those of the SS (185/210: 88%, 87%, and 73%, respectively) and CS (68/81: 84%, 74%, and 69%, respectively) groups. The pregnancy rates of heifers that received an embryo were not significantly different among HS, SS, and CS groups (45/82: 55%, 78/153: 51%, and 25/56: 45%, respectively). However, because the yield rate of acceptable recipients in the HS group was higher than in the other groups, the final pregnancy rates (no. pregnant/no. synchronization treatment) of the HS group (50%) was significantly higher than those of the SS and CS groups (37%; P < 0.05, and 31%; P < 0.01, respectively). Taken together, these findings demonstrate that the HS protocol is effective for estrus&#8211;ovulation synchronization of Holstein heifers, thus improving the productivity of ET by increasing the yield rates of heifers with a functional CL which leads to acceptable pregnancy results. 
ER  -

