138 Relationships Between Antral Follicle Count, Ovarian Volume, Pre-Antral Follicle Number, and Oocyte Quality

Abstract

The objective was to evaluate the possible relationships between AFC, ovarian volume, ovarian follicle reserve and oocyte quality in abattoir-derived ovaries (experiment 1) and in cows (experiment 2) submitted to OPU. Antral follicle counts of ≥25, 16 to 24, and ≤ 16 were used to define AFC classes as high (HAFC), intermediate (IAFC), and low (LAFC) in both experiments. In experiment 1, after antral follicles were aspirated, abattoir ovaries (n = 10 per AFC class) were processed by conventional histology and pre-antral follicles were counted within primordial, primary, secondary, and tertiary classes and classified as either healthy or degenerate under regular microscopy (Cushman et al. 1999). In experiment 2, HAFC (n = 42), IAFC (n = 34), and LAFC (n = 29) cows were submitted to OPU and oocytes classified as grades 1, 2, and 3 or degenerate (IETS, 2010). Antral follicles (≥3 mm in diameter) were counted by ultrasonography. Data were analysed by GENMOD and GLM procedures of SAS (SAS Institute Inc., Cary, NC, USA) after transformations, when required. In experiment 1, mean normal primordial follicle number was higher (P < 0.001) in HAFC (137.0 ± 1.6)a compared with IAFC (52.6 ± 1.9)b and LAFC (20.2 ± 5.3)c ovaries. However, the mean number of degenerate primordial follicles was lower (P < 0.001) in low count ovaries (2.4 ± 0.6) compared with HAFC (19.0 ± 4.7) and IAFC (16.4 ± 1.5, P < 0.001). Normal primary follicle number was higher in the HAFC compared with IAFC and LAFC ovarian classes (86.2 ± 7.0a v. 34.6 ± 5.1b and 14.4 ± 3.3c, respectively; P < 0.01). Degenerate primary follicles were higher in the HAFC compared with LAFC ovarian class (16.8 ± 6.5 v. 5.2 ± 2.64; P < 0.05). Normal secondary follicle number was also higher in the HAFC compared to LAFC ovarian classes (25.2 ± 7.67 v. 2.4 ± 0.8; P < 0.05). The number of degenerate secondary follicles differed (P < 0.01) only between the IAFC and the LAFC ovarian classes (0.6 ± 0.4 and 7.2 ± 2.4, respectively), which were similar (P > 0.5) to the HAFC class (3.8 ± 1.0). In experiment 2, grade 1, 2, and 3 oocytes, viable oocytes, and ovarian volume (mm3) were higher (P < 0.001) in HAFC compared with IAFC and LAFC cows (grade 1: 7.9 ± 0.6a, 4.9 ± 0.7b and 3.3 ± 0.7c; grade 2: 4.0 ± 0.4a, 2.8 ± 0.4b and 1.2c; grade 3: 2.1 ± 0.4a, 2.5 ± 0.4a and 1.3 ± 0.5b, respectively; viable oocytes: 16.3 ± 1.1a, 13.1 ± 1.2b, and 8.1 ± 1.3c, respectively; (volumes: 12.6 ± 0.7a, 10.1 ± 0.8b, and 8.1 ± 0.9c, respectively). In conclusion, high AFC is linked to a higher follicular reserve, oocyte quality, and ovarian volume. It is safe to apply AFC in the selection of bovine females without compromising oocyte or pre-antral follicular population qualities.