Use of FSH in two different regimens for ovarian superstimulation prior to ovum pick up and in vitro embryo production in Holstein cows

- FSH stimulation increased the number and the proportion of medium-sized follicles for OPU in non-lactating Holstein cows.
- The use of FSH stimulation in four or six administrations resulted in similar OPU-IVP efficacy.
- Cows with high follicle population have 90% increase in the number of blastocysts and tended to have lower blastocyst rate.

We aimed with the present study to evaluate the effects of FSH treatment (200 mg) split in four or six administrations on ovarian follicle stimulation and in vitro oocyte competence for embryo production in dairy cows with synchronized follicular wave emergence. On random days of the estrous cycle (Day 0), non-lactating Holstein cows received a progesterone (P4)-releasing intravaginal device and 2 mg estradiol benzoate IM. On Day 3, they received 0.530 mg sodium cloprostenol (PGF2α) IM. Control cows (n = 35) received no further treatments, whereas FSH-treated cows received 200 mg FSH split in four (FSH4 group; n = 33) or six (FSH6 group; n = 33) administration regimens. Starting on Day 4, cows in FSH4 group received 200 mg FSH split in four equivalent doses of 50 mg 12 h apart. Cows in FSH6 group received the same total FSH dose split in six equivalent doses of 33.3 mg 12 h apart, but treatments started on Day 3. On Day 7 AM (36 h of “coasting” period for FSH-treated groups), the P4 devices were removed and cows were subjected to ovum pick up (OPU). Viable oocytes were in vitro fertilized using sexed-sorted semen. Although FSH treatment did not (P > 0.1) increase the total number of follicles (Control, 53.2 ± 4.5 vs. FSH-treated, 51.4 ± 3.1), the two hormonal stimulation regimens, FSH4 and FSH6, increased the number of medium follicles (6-10 mm; 5.2 ± 0.5 vs. 18.1 ± 1.4; P < 0.0001) and reduced the number of small follicles (2-5.9 mm; 46.3 ± 5.1 vs. 31.0 ± 2.4 P < 0.0001). Also, FSH treatment or regimen did not increase (P > 0.1) the number of viable oocytes (Control, 12.6 ± 1.26 vs. FSH-treated, 12.70 ± 1.03), recovery rate (Control, 36.5% vs. FSH-treated, 36%) and the number of in vitro produced blastocyst (Control, 4.1 ± 0.52 vs. FSH-treated 4.3 ± 0.5). We concluded that FSH stimulation protocol proposed herein is effective to stimulate the growth of small antral follicle population prior to OPU, but it was ineffective to improve in vitro oocyte competence for embryo production in non-lactating Holstein cows with synchronized follicular wave emergence.