Ovarian stimulation alternatives for in vitro production of embryos in water buffaloes

BADEO, ALEXIS; KONRAD, JOSÉ LUIS; VALLEJOS, NATALIA; PONCE, PABLO; SANSINENA, MARINA; CRUDELI, GUSTAVO; MALDONADO-VARGAS, PABLO

REVISTA CIENTíFICA

UNIV ZULIA

Año: 2023 vol. 33

0798-2259

Currently, one of the most promising tools to increase the number of transferable embryos in buffaloes is in vitro production (IVP). However, IVP still has certain limitations that prevent its optimal efficiency for commercial application. One of these limitations is the reduced number and low competence of oocytes obtained from transvaginal follicular aspiration in this species. It has been found that ovarian stimulation with follicle-stimulating hormone (FSH) before aspiration improves the technique´s efficiency, primarily due to the increased competence of the obtained oocytes. The objective of this study was to evaluate the response to different hormonal stimulation treatments in buffalo donors, their effect on oocyte quality, and subsequent embryo production. This field study was conducted at the Pedro Antonio Silva buffalo farm, located in the General Paz department, Province of Corrientes, in 2021. A total of 60 OPU sessions were performed on Murrah and Mediterranean breed donors, and four ovarian stimulation treatments were applied. Treatment (TRT) 1, which was used as control (n=20), consisted of a day 0 insertion of an intravaginal progesterone device (IP) + 2 mg estradiol benzoate (EB) i.m., with OPU performed on day 7. Treatment (TRT) 2 (n=10) consisted of day 0 insertion of IP + 2 mg EB, followed by four applications of FSH (Folltropin-V®) i.m. with a total of 160 mg distributed in decreasing doses every 12 hours for two days (50mg, 50mg, 30mg, 30mg), OPU was then performed 36 hours after the last application. Treatment (TRT) 3 (n=20) consisted of day 0 insertion of IP + EB, followed by a day 4 application of 1050 IU of recombinant eCG (FoliRec®) i.m., OPU was performed on day 7; Treatment (TRT) 4 (n=10) consisted of day 0 insertion of IP + EB, followed by day 4 application of 2500 IU of serum eCG (Ecegon®) i.m., OPU was performed 72 hours later. Prior to each follicular aspiration, antral follicles were counted using a portable ultrasound with a linear probe (Mindray, DP30-Vet) and classified into small (=3mm Ø), medium (4-8 mm Ø), and large (>8mm Ø) follicles. The aspirated oocytes or COCs (cumulus-oocyte complexes) were classified into grades (1 to 4) based on the number of cumulus layers present, according to the International Embryo Transfer Society method (IETS Manual). In vitro fertilization (IVF) was performed after 24 hours of oocyte in vitro maturation using cryopreserved semen from buffalo bulls of proven fertility. In vitro culture (IVC) was carried out for 6.5 days, and all embryos that reached the blastocyst stage were graded and vitrified. Descriptive statistics and analysis of variance were conducted on the obtained data, considering population and follicular size, quantity and quality of oocytes, and embryo production, with a significance level (a) of 5%. The total observed follicular population did not differ among treatments (p>0.05). However, stimulation in TRT2 (FSH) and TRT4 (serum eCG) increased the proportion of medium-sized follicles (4-8mm) available for OPU (p