Ovarian follicular dynamics in the llama

Ovarian follicular dynamics were determined in adult llamas by ultrasonography and palpation per rectum and hormone analysis (estradiol-17 beta and estrogen conjugates) of plasma and urine. The relationship of gonadotropin secretion to follicular development was determined by the analysis of plasma FSH and LH concentrations. Progesterone analysis of plasma was used to verify or deny the presence of CL. Final follicular development (from 3 mm) averaged 4.8 days, while the duration of the mature follicle (8-12 mm) averaged 5.0 days; regression of the follicle occurred over about 4 days. The development of a subsequent dominant follicle usually began within 2-3 days after onset of regression of the dominant follicle. While several follicles were present at the time of the demise of the dominant follicle, only one follicle continued to develop. The interval between ovarian follicle waves averaged 11.1 days. Dominant follicle activity alternated between ovaries in 81% of the cycles. The occurrence of dominant follicles was evenly distributed between ovaries. While plasma estradiol and estrogen conjugate concentrations were positively associated (p less than 0.05) with follicular activity, urinary estrogen conjugate concentrations best reflected ovarian follicular dynamics (p less than 0.001). Daily FSH concentrations in plasma were not correlated with follicular activity. LH concentrations in plasma were low in all animals throughout the study, indicating estrogen from developing ovarian follicles does not induce the release of LH. Progesterone values were low during the study, indicating that the llama does not spontaneously ovulate, at least under the conditions of this study. In summary, llamas have overlapping ovarian follicle waves that occur at about 11-day intervals.(ABSTRACT TRUNCATED AT 250 WORDS)