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Anim Reprod Sci. 2014 Oct;149(3-4):345-52. doi: 10.1016/j.anireprosci.2014.08.001. Epub 2014 Aug 17.

The effect of repeated administrations of llama ovulation-inducing factor (OIF/NGF) during the peri-ovulatory period on corpus luteum development and function in llamas.

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Department of Animal Science, Faculty of Veterinary Sciences, Universidad Austral de Chile, Valdivia, Chile.
Escuela de Medicina Veterinaria, Facultad de Recursos Naturales, Universidad Católica de Temuco, Temuco, Chile.
Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Canada.
Departamento de Histología y Anatomía, Universidad Austral de Chile, Valdivia, Chile.
Department of Veterinary Biomedical Sciences, Ross University School of Veterinary Medicine, Basseterre, St. Kitts, West Indies. Electronic address:


The objective of the study was to test the hypothesis that repeated administrations of OIF/NGF during the peri-ovulatory period (pre-ovulatory, ovulatory, early post-ovulatory), will enhance the luteotrophic effect in llamas. Female llamas were examined daily by transrectal ultrasonography in B- and Doppler-mode using a scanner equipped with a 7.5-MHz linear-array transducer to monitor ovarian follicle and luteal dynamics. When a growing follicle ≥7mm was detected, llamas were assigned randomly to one of the three groups and given 1mg of purified OIF/NGF im (intramuscular) (a) pre-ovulation (single dose; n=12), (b) pre-ovulation and at the time of ovulation (2 doses, n=10), or (c) pre-ovulation, at the time of ovulation, and 24h after ovulation (3 doses, n=10). The pre-ovulatory follicle diameter at the time of treatment, ovulation rate and the first day of CL detection did not differ (P=0.3) among groups. However, maximum CL diameter was greatest (P=0.003) in llamas in the 2-dose group, and smallest in the 3-dose group. Accordingly, the 2 dose-group had the largest day-to-day profile for CL diameter (P<0.01), area of CL vascularization (<0.01), and plasma progesterone concentration (P=0.01) compared to the other groups. Interestingly, the luteal response to 3-doses of OIF/NGF during the peri-ovulatory period was not different from a single dose. In conclusion, OIF/NGF isolated from llama seminal plasma is luteotrophic and the effect on CL size and function is affected by the number and timing of treatments during the peri-ovulatory period.


Corpus luteum; Llamas; Nerve growth factor; Ovulation-inducing factor

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