179 CORPUS LUTEUM DEVELOPMENT AFTER FOLLICLE ASPIRATION IS RELATED TO CHARACTERISTICS OF THE ASPIRATED FOLLICLE IN DAIRY COWS

Abstract

The aim of this study was to investigate whether morphology or function of a corpus luteum (CL), which developed after an aspiration of a preovulatory follicle, is related to follicular characteristics such as size or steroid content. If so, CL morphology or function could be used as a retrospective quality parameter for the aspirated follicle or the follicular characteristics as a prospective parameter for the quality of the developing CL. Therefore, 44 aspiration sessions were performed using 18 cows between 26 and 121 days after parturition during the first lactation. Heat was induced in mid-dioestrus with Cloprostenol. A GnRH analogon (Depherelin) were administrated 54 h later. The dominant follicle was aspirated 21 h after administration of the GnRH analogue. The diameter of the dominant follicle at aspiration and the cross-section area of the resulting luteal tissue 14 days later were measured by ultrasound. Concentrations of progesterone (P4) and 17-β-oestradiol (E2) in blood and follicular fluid (FF) were determined by H3-RIA. A CL development occurred in 82% of aspiration sessions after aspirating the dominant follicles. The interval of time between parturition and follicle aspiration did not affect variables investigated. As expected, cross-section area of the luteal tissue was positively correlated with plasma P4 concentration on Day 14 after follicle aspiration (r = 0.54; P < 0.01). The diameter of the aspirated follicle was positively correlated with the plasma P4 concentration on Day 14 after follicle aspiration (r = 0.52; P = 0.02), but the diameter was not correlated with the cross-section. Comparing the FF of follicles that originated a CL after aspiration with follicles that did not, both types had comparable P4 concentrations (578 ± 79 ng mL–1 v. 398 ± 84 ng mL–1; P = 0.2), but the former type presented higher E2 concentrations (206 ± 23 ng mL–1 v. 64 ± 29 ng mL–1, P < 0.01) compared with the latter. The P4 concentrations in FF of follicles that originated a CL after aspiration were positively related to cross-section area of the CL (r = 0.48; P = 0.04), but neither P4 nor E2 concentrations in the FF of preovulatory follicles could be used as a predictor for the plasma P4 concentration at day 14. In conclusion, CL development after follicle aspiration can be used as a retrospective quality parameter of aspirated dominant follicles. Preovulatory follicle diameter as well as cross-section area of the luteal tissue could be used prospectively to identify cows with high plasma P4 levels, and this may help to identify suitable recipients for embryo transfer. This study was supported by the German Research Foundation (DFG WE 2458/7-2).