390 THE EFFECT OF REDUCED FSH DOSE AND NUMBER OF TREATMENTS ON SUPEROVULATORY RESPONSE IN CIDR-TREATED KOREAN NATIVE COWS

Abstract

Reducing the total dose and numbers of treatments with FSH for superstimulation without decreasing embryo yield may be less stressful and more economical for bovine embryo transfer. The objective of this study was to investigate the effect of dose and the number of days of FSH treatment on superovulatory responses in CIDR-treated Korean native cows. Forty-two cows, at random stages of the estrous cycle, received a CIDR device (CIDR^TM; InterAg, Hamilton, New Zealand), 1 mg estradiol benzoate (SY Esrone; Samyang, Seoul, Korea) and 50 mg progesterone (SY Ovaron; Samyang); gonadotropin treatment began 4 days later. Cows were divided into 2 groups based on the dose and numbers of days of treatment with porcine FSH (pFSH): T1 group (n = 20): a total of 28 mg pFSH (recommended dose of Antorin^®; Kawasaki Pharmaceutical, Tokyo, Japan) was given in twice daily IM injections in decreasing doses over 4 days (5, 5, 4, 4, 3, 3, 2, and 2 mg); and T2 group (n = 22): a total of 24 mg pFSH given in twice daily decreasing doses over 3 days (5, 5, 4, 4, 3, and 3 mg). Otherwise, all cows received the same treatments. Twenty-five and 15 mg dinoprost (PGF_2α; Lutalyse; Pharmacia & Upjohn, Puurs, Belgium) were given with the 5th and 6th injections of pFSH, respectively. CIDR devices were withdrawn with the 6th pFSH injection, and the cows received 100 µg Gonadorelin (GnRH; Fertagyl; Intervet, Boxmeer, The Netherlands) 36 h after CIDR device removal. Cows were artificially inseminated using commercial semen from 4 Korean native bulls twice, at 48 and 60 h after CIDR device removal, and embryos were recovered 6 or 7 days after the 2nd insemination. The number of CL was counted on the day of embryo recovery by transrectal ultrasonography (Sonovet 600 with 5.0 MHz linear-array transducer; Medison Co., Ltd., Seoul, Korea). The recovered embryos were evaluated according to the IETS Manual for stage of development and quality. All data between groups were compared using Student's t-test. The numbers of CL (9.7 ± 1.1 vs. 9.4 ± 1.3), total ova/embryos (7.2 ± 1.1 vs. 6.3 ± 1.4), transferable embryos (4.4 ± 1.0 vs. 3.6 ± 0.9), degenerate embryos (0.9 ± 0.3 vs. 1.3 ± 0.4), and unfertilized ova (2.0 ± 0.6 vs. 1.5 ± 0.5) did not differ between groups (T1 vs. T2), respectively (P > 0.05). Data indicate that the reduced dose (24 vs. 28 mg) and numbers of treatments (6 vs. 8) of pFSH for superstimulation of Korean native cows does not affect the embryo yield.