182 EFFECT OF OVULATION-INDUCING FACTOR ON DEVELOPMENT AND VASCULAR PERFUSION OF THE OVULATORY FOLLICLE AND CORPUS LUTEUM IN LLAMAS

Abstract

The aim of the study was to determine if purified ovulation-inducing factor (OIF) from llama seminal plasma evokes changes in tissue vascular area of the preovulatory follicle and CL. Mature non-lactating, non-pregnant, female llamas (n = 20) were monitored by transrectal ultrasonography using a 7.5-MHz linear-array transducer (MyLab 5, Canadian Veterinary Imaging) to determine ovarian follicular status. Llamas with a growing follicle (for 3 consecutive days) ≥8 mm were assigned randomly to 2 groups (n = 10/group) and given an i.m. dose of (1) 50 µg of gonadorelin acetate or (2) 1 mg of purified OIF from llama seminal plasma. Llamas were examined daily by transrectal ultrasonography using B-mode and power Doppler mode from Day 0 (day of treatment) to Day 16 to detect ovulation and CL development, and to calculate the area of blood-flow signal in the preovulatory follicle at 12 h after treatment and in the CL on Days 2, 4, 6, 8, 10, 12, 14, and 16. Power Doppler images were recorded, edited, and analysed using the ImageJ software (National Institutes of Health, Bethesda, MD, USA). Data were compared between groups by Student t-test, chi-square, and ANOVA for repeated measures. No differences were detected between GnRH and OIF groups, respectively, in the diameter of the preovulatory follicle at the time of treatment (9.7 ± 0.3 v. 9.9 ± 0.4 mm), ovulation rate (10/10 v. 10/10), interval from treatment to ovulation (32.0 ± 0.6 v. 30.4 ± 1.8 h), maximum CL diameter (13.05 ± 0.4 v. 13.5 ± 0.3 mm), or the day on which the CL reached the maximum diameter (8.7 ± 0.3 v. 8.2 ± 0.2). The preovulatory follicle from llamas treated with purified OIF had a greater (P ≤ 0.0001) blood-flow signal area after treatment than that of the GnRH group. Similarly, the luteal tissue of llamas treated with purified OIF had a greater (P ≤ 0.001) blood-flow signal area than that of the GnRH group on Days 4, 6, 12, and 16 after treatment. We conclude that OIF purified from llama seminal plasma increases the vascular perfusion of the preovulatory follicle and the subsequent CL, consistent with the hypothesis that OIF is luteotrophic. Research funded by Chilean National Science and Technology Research Council (Fondecyt Regular 1120518), the Natural Sciences and Engineering Research Council of Canada, and the Alpaca Research Foundation.