Short intervals between ultrasonographically guided follicle aspiration improve oocyte quality but do not prevent establishment of dominant follicles in the Gir breed (Bos indicus) of cattle

The aim of the present study was to evaluate oocyte recovery and embryo yield using two different ovarian follicular aspiration schedules in donor cows of the Gir breed. Pluriparous, non-lactating Gir cows (n=14) were randomly allocated to one of two groups, one of which had aspirations of ovarian follicular contents conducted once a week (TVFA-1x) and the other twice weekly (TVFA-2x), for nine consecutive weeks. Before follicle aspiration, follicular population was recorded in three classes according to size (>6 mm, 6–9 mm and >9 mm). The cumulus–oocyte complexes (COCs) recovered were identified, morphologically classified and in vitro matured, fertilized with Gir sperm and cultured in CR2 medium for 7 days. There was no difference (P>0.05) in the size of the largest follicle, number of follicles identified or follicular content aspirations between TVFA-1x and TVFA-2x groups. Large follicles (>9 mm) were observed for all the aspiration intervals considered (3, 4 or 7 days). More oocytes were recovered per session in TVFA-1x as compared with TVFA-2x (8.9±0.8 versus 7.0±0.7, P<0.01), resulting in a greater recovery rate in this group (74.3% versus 58.7%, P<0.01). More COCs of Grade I were recovered from TVFA-2x (22.6% versus 13.3%, P<0.01). There was no difference in cleavage rate between groups, but the percentage of embryos that reached the blastocyst stage was greater in TVFA-2x as compared with the TVFA-1x (31.8% versus 21.6%, P<0.01). The greater in vitro performance qualities of TVFA-2x oocytes compensates for the greater oocyte recovery rate in TVFA-1x, demonstrating a greater embryo production potential. Despite showing uncommon follicular dynamics characteristics when subjected to follicular aspiration, Gir cows can be successfully used as oocyte donors for in vitro embryo production.