Gregg P Adams
It has always been thought that the physical act of mating and the orgling noise made by the males induces ovulation in female alpacas. However it turns out that there is an ovulation inducing factor in alpaca semen.
Here are the results of the research, funded by the Alpaca Research Foundation in the USA and carried out by Gregg P Adams DVM, PhD, from the Western College of Veterinary Medicine, University of Saskatchewan, Canada.
Camelids have been categorized as induced ovulators and present dogma suggests that physical stimulation during copulation is primarily responsible for eliciting ovulation. Recent discoveries, however, challenge this dogma. The project focuses on the isolation and characterization of an ovulation-inducing factor (OIF) present in the seminal plasma of camelids. The factor was initially reported in Bactrian camels, but has not been documented in any other species.
Studies were conducted to document the existence of an OIF in the seminal plasma of alpacas and llamas. In Experiment 1, female alpacas were given alpaca seminal plasma or saline intramuscularly or by intrauterine infusion. Only alpacas that were given seminal plasma intramuscularly ovulated (93%). In Experiment 2, ovulation was detected in 90% llamas at a mean of 29 hours after seminal plasma treatment. Plasma progesterone concentrations were maximal 9 days after treatment and back to minimum at 12 days after treatment. In Experiment 3, females were given seminal plasma, GnRH (positive control), or saline (negative control), and ovulation was detected in 100%, 83% and 0% in the respective groups. Blood samples taken every 15 minutes for 8 hours after treatment revealed that seminal plasma caused circulating luteinizing hormone (LH) to become elevated within 1 hour and remain elevated for over 8 hours. Compared to the GnRH group, the corpus luteum (CL; progesterone-producing gland in the ovary necessary for maintenance of pregnancy) grew larger and plasma progesterone concentration was twice as high in the seminal plasma group. Results show, for the first time, that a potent ovulation-inducing factor is present in the semen of alpacas and llamas. Treatment-induced ovulation was associated with a surge in circulating concentrations of LH and enhancement of CL form and function.
The existence and nature of this factor has direct implications on fertility, infertility, breeding management, and commercial development of therapeutic drugs for alpacas. The evolutionary conservation of such a factor raises the possibility of its existence in other induced and spontaneously ovulating species; hence, the characterization of OIF in the seminal plasma of alpacas may have much broader implications. Further studies are being conducted to isolate and characterize the chemical in semen of alpacas and to determine if it is present in other species.
Publications as a result of Alpaca Research Foundation funding:
Adams GP, Ratto MH, Huanca W, Singh J (2005) Ovulation-inducing factor in the seminal plasma of alpacas and llamas. Biology of Reproduction 73:452-457.
Ratto MH, Huanca W, Huanca T, Singh J, Adams GP (2004) Ovulation-inducing factor in seminal plasma: species comparison and molecular weight determination. Proceedings of the annual meeting of the Society for the Study of Reproduction, Vancouver, BC August 2004, Abstract 181.
Adams GP, Ratto MH, Singh J (2004) Ovulation-inducing factor in the seminal plasma of llamas. International Congress on Animal Reproduction, Porto Seguro, Brazil August 2004, p 217.
Ratto MH, Huanca W, Singh J, Adams GP. (2005). Effect of OIF on ovulation rate and luteal development in llamas. 1st Annual Reproductive Science and Medicine Research Symposium. March 3, 2005, p 18. (Best basic science paper, 2nd Place)