Follicular growth, ovulation and embryo recovery in dairy cows given FSH at the beginning or middle of the estrous cycle.

Variability in the superovulation response is an important problem for the embryo transfer industry. The objective of this study was to determine whether FSH treatment at the beginning of the cycle would improve the ovulation rate and embryo yield in dairy cows. Twenty-eight postpartum cyclic dairy cows were allocated at random to 4 treatment groups (A, B, C and D). Group A cows (n=10) received FSH (35 mg) at a decreasing dose, starting on Day 9 (Day 0=day of estrus) for 5 days followed by PGF2alpha (35 mg) on Day 12. Cows assigned to Groups B, C and D (n=6 cows each, respectively) were given 35 mg FSH at a decreasing dose from Days 2 to 6 followed by PGF2alpha on Day 7. Group C and D cows received PRID inserts from Day 3 to Day 7. Cows in Group D additionally received 1000 IU hCG 60 hours after PGF2alpha treatment. Ovaries were scanned daily using a real time ultrasound scanner from the beginning of FSH treatment until embryo recovery, to monitor follicular development, ovulation and the number of unovulated follicles. Embryos were recovered from the uterus by a nonsurgical flushing technique 7 days after breeding. There were no differences (P>0.01) in the number of follicles>10 mm at 48 hours after PGF2alpha treatment among the 4 groups. The mean numbers of follicles were 10.6+/-1.2, 9.3+/-1.3, 12.2+/-1.3 and 15.0+/-2.9 for Groups A, B, C and D, respectively. A significantly (P<0.001) higher number of ovulations was observed and a larger number of embryos was recovered in Group A than in the other groups. The results of this study indicate that superovulation with FSH at the beginning of the cycle causes sufficient follicular development but results in very low ovulation and embryo recovery rates.