Abstract
The objective of this study was to investigate the effect of dosage and number of days of FSH treatment on superovulatory response in controlled internal drug release (CIDR)-treated Korean native cows. Forty cows underwent two superovulatory treatments with a crossover design. Cows, at random stages of the estrous cycle, received a CIDR together with injections of 1 mg estradiol benzoate and 50 mg progesterone, and gonadotropin treatment began 4 days later. The cows were divided into 2 groups based on the dosage and number of days of treatment with porcine FSH (FSH); a total of 28 mg FSH was given in twice daily intramascular injections in decreasing doses over 4 days (5, 5, 4, 4, 3, 3, 2 and 2 mg; T1 group, n=20) or a total of 24 mg FSH was given in twice daily decreasing doses over 3 days (5, 5, 4, 4, 3 and 3 mg; T2 group, n=20). This was followed by the alternate treatment in the subsequent superovulation. The cows were treated identically in all other respects. PGF2 α (25 mg and 15 mg) was given with the 5th and 6th injections of FSH, CIDR were withdrawn at the 6th FSH injection and the cows received 200 hcvg GnRH 36 h after CIDR withdrawal. The cows were artificially inseminated twice, at 48 and 60 h after CIDR withdrawal, using commercial semen from four Korean native bulls, and embryos were recovered 6 or 7 days after the 2nd insemination. The numbers of corpora lutea (CL; 7.9 ± 1.0 vs. 8.3 ± 1.1) and large follicles (1.2 ± 0.2 vs. 1.3 ± 0.3) present at the time embryo recovery, as detected by ultrasonography, did not differ between the T1 and T2 groups (P>0.05). Similarly, the numbers of total ova/embryos (6.2 ± 0.9 vs. 6.4 ± 1.1), transferable embryos (3.4 ± 0.8 vs. 3.2 ± 0.7), degenerate embryos (0.8 ± 0.2 vs. 1.0 ± 0.3) and unfertilized ova (2.1 ± 0.5 vs. 2.2 ± 0.5) did not differ between the groups (P>0.05). These data indicate that a reduced dose (24 vs. 28 mg) and number of treatments (6 vs. 8) of FSH for superovulation of CIDR-treated Korean native cows does not affect the embryo yield.
