Synchronization of time of ovarian follicular development in llamas (Lama glama) using a protocol based on GnRH and...

The aim of this study was to evaluate the effectiveness of a protocol based on GnRH and PGF_2α to synchronize the emergence of a new wave of ovarian follicular development in llamas and, therefore, when a new dominant follicle develops. Llamas (n = 18) were assigned to growing, mature or regressing follicle groups according to the phase of the follicular wave at the beginning of treatment. The protocol was initiated with a GnRH analogue (GnRHa) injection on Day 0 followed 7 days later with a d-cloprostenol injection and a second GnRHa injection on Day 10. Ovulation rate after the first GnRHa treatment, day of new follicle emergence, mean plasma progesterone concentration and percentage of animals with a newly developed dominant follicle ≥ 7 mm on Day 10 were evaluated. Ovulation rate after the first GnRHa was less in the regressing than mature and growing follicle groups and new follicular wave emergence occurred earlier in the regressing follicle group than in the other two groups. Mean plasma progesterone concentration in females that had ovulations after the first GnRHa injection was similar. The percentage of animals that had a new follicle ≥ 7 mm on Day 10 was not different among groups and the overall percentage was 66.6%. The total synchronization rate for development of a new wave of follicular development on Day 10 was greater in females having ovulations after the first GnRHa injection than in those that did not have ovulations. In conclusion, the protocol used in the present study was useful for synchronizing ovarian follicular development in 66% of the llamas regardless of the phase of the follicular wave development at the beginning of treatment.