Limitations of ultrasound guided follicular aspiration for analysis of ovarian follicular fluid in dairy cattle

The aim of this study was to evaluate the applicability of ovum pick-up equipment for follicular fluid collection from various follicular structures (experiment 1) and for recovery of follicular fluid for acid-base balance analysis (experiment 2). An ultrasound scanner equipped with a 5-MHz convex transducer was used for transvaginal ultrasound-guided follicular aspiration. A 17-gauge, 60-cm aspiration needle was connected with a shortened aspiration line. The fluid was aspirated manually into a 2 mL plastic syringe at a speed of approximately 0.2 mL/s. The success of aspiration was higher in ovarian cysts (100%) and single follicles larger than 13 mm (76.7%) compared to single follicles smaller than 12 mm (20%, p less than 0.001). The success of aspiration of multiple follicles on day 4 (diameter of 7-9 mm) was higher (90.9%) compared to follicles on day 2 (diameter of 4-6 mm) (66.7%, p less than 0.05) in experiment 1. The fluid from ovarian cysts more than 25 mm in diameter was aspirated in a two-step procedure (samples 1 and 2) for the determination of pH, HCO3, BE, pCO2 and pO2 (experiment 2). The indicators were compared between samples 1 and 2. Higher pO2 as well as pH and lower pCO2 in sample 1 compared to sample 2 showed insufficient anaerobic conditions during the first phase of the puncture in experiment 2. Our study brings for the first time the finding that the ovum pick-up equipment used in our experiments is suitable for the collection of follicular fluid only from larger follicular structures. The sampling of follicular fluid for acid-base balance assays requires the development of a special new device to prevent samples from coming into contact with air during aspiration.