Inhibitory effect of progesterone on the development of the follicular wave in llamas

© 2002 Universidad Nacional Mayor de San Marcos. All rights reserved. The effect of the exogenous progesterone (P4) on the development of follicular waves in llamas was studied in twenty-five females. According to dose and regimen for P4 administration, animals were allocated to 5 groups (n=5): 00 (control group), G 1 (30 mg P/day for 2 days); G2 (30 mg P/day for 4 days); G3 (50 mg P/day for 2 days) and G4 (50 mg P/day for 4 days). Development of dominant ():.7 mm) and subordinated follicles (>3 mm and <7 mm) were monitored daily by transrectal ultrasonography. The minimun size reachedbythedorninantfollicleingroupsGl (4.6±0.9mm), G3(5.1±1.5 mm) andG4(5.3 ± 1.6 mm) were smaller (P< 0.05) than group 00 (8.5 ± 1.0 mm). The whole follicular regression of the dominant follicle in groups G 1 (5.5 ± 2.0 mm), G2 (5.9 ± 1.4 mm) and G3 (5.3 ± 3. 3 mm) were larger (P< 0.05) than group 00 (0.9 ± 1.4 mm). The number of subordinated follicles hada significative increase (P< 0.05) in groups G 1 and G4, on days 2 and 3 in relation to days 7 and 8 post-treatment. Results demonstrate that exogenous progesterone inhibits the development of the dominant and subordinate follicles in llamas during treatment days; however, immediately after the end of the treatment, the · number of subordinate follicles increases, due to the regression of the dominant follicle in order to allow the emergence of a new follicular wave.