Oocyte IVM is a long process during which oocytes acquire their ability to support the stages of development in a stepwise manner, ultimately reaching activation of the embryonic genome. The overall success of this process can be affected by factors such as hormonal treatment for ovarian stimulation. Thus, the current study aims to evaluate the possible effects of the ovarian stimulatory protocols on the goat oocyte quality and IVM rate. Adult and cyclic Canindé goats were heat-synchronized by means of intravaginal sponges impregnated with 60 mg medroxyprogesterone acetate (MAP, Progespon, Syntex, Buenos Aires, Argentina) inserted for 11 days coupled with a luteolytic injection of 50 μg cloprostenol (Ciosin, Coopers, São Paulo, Brazil) in the 8th day of treatment. The ovarian stimulation was carried out using one of the following protocols: a) standard multi-doses (MD) with 120 mg pFSH (Folltropin-V, Vetrepharm, Canada) distributed in five injections (30/30; 20/20; 20 mg) at 12 h intervals (n = 18); b) three- doses (TD) with 120 mg pFSH administered in three injections (60; 40; 20 mg) at 24 h intervals (n = 17); c) one shot (OD) of 70 mg pFSH plus 200 IU of eCG (Novormon, Syntex) administered 36 h before sponge removal (n = 17). In MD andTD groups, the pFSH injections started in Day 8 of progestagen treatment. The follicles were aspirated just after the sponge removal using laparoscopic oocyte recovery (LOR). This procedure was performed with a 22-gauge needle and a vacuum pump at 30 mmHg. The collection medium was TCM-199 supplemented with HEPES (10 mM), heparin (20 IU mL-1), and gentamicin sulfate (40 μg mL-1). COCs were classified as grade I, II, III, or IV based on visual criteria (Baldassarre H et al. 2003 Theriogenology 56, 831-839). Good quality oocytes (grade I and II) were incubated in TCM-199 supplemented with cysteamine (100 μM), EGF (10 ng mL-1) and gentamicin sulfate (40 μgm L-1) at 38.5°C in a humidified atmosphere with 5% CO2 in air for 24 h. Oocyte maturation was assessed by the visualization of first polar body under inverted microscope. Data were expressed as percentages and analyzed using the Fischer’s exact test. No statistical differences among hormonal treatments (P > 0.05) were observed for the percentage of the good quality oocytes, with 70.4 ± 3.0% of COCs graded in I and II. The IVM rate inTD (31.4%) was statistically lower than MD (31.4% v. 46.5%, P = 0.04) group. However, no significant differences (P = 0.89) were observed between OD (45.2%) and MD groups. Thus, current results indicate that oocyte production for IVM can be facilitated using ovarian stimulation with the one shot FSH/eCG regime without affecting meiotic competence. In summary, OD and MD treatments can be used for oocyte IVM in an embryo production programme in Canindé goats.
This study was supported by the following Brazilian agencies: FINEP, CNPq, FUNCAP, and CAPES.
Polar body morphology and spindle imaging as predictors of oocyte quality
