Induced ovulation (animals)

Induced ovulation is when a female animal ovulates due to an externally derived stimulus during, or just prior, to mating, rather than ovulating cyclically or spontaneously. Stimuli causing induced ovulation include the physical act of coitus or mechanical stimulation simulating this, sperm and pheromones.

In cats

Domestic cats are often described as induced ovulators. During intromission, the penis probably causes distension of the posterior vagina and induces release of gonadotropin releasing hormone (GnRH) from the hypothalamus via neuroendocrine reflexes. A surge of luteinising hormone (LH) occurs within minutes of mating. With multiple matings, the LH surge is greater and lasts longer than when only one mating occurs. There are reports of ovulation without mating in cats. Spontaneous ovulation not only occurs in cats, but occurs with some frequency. It appears that non-copulatory ovulation may be possible in response to a variety of visual, auditory or olfactory cues. It is more appropriate to consider domestic cats to be both an induced and spontaneous ovulator.[1]

In rabbits

It has been known since 1905[2] that domestic rabbits are physically induced ovulators, although they may also ovulate spontaneously. Early reports stated that simply having an oestrous doe in close proximity to a buck can induce ovulation, although there were no data presented in these early reports.[3]

In camelids

Dromedary camels (Camelus dromedarius), bactrian camels (Camelus bactrianus), llamas (Lama glama) and alpacas (Lama pacos) are all induced ovulators.[4]

Bactrian camel

Bactrian camels ovulate after insemination of semen into the vagina; it is the seminal plasma, but not the spermatozoa, which induces ovulation. Ovulation occurs in 87% of females after insemination: 66% ovulate within 36 h and the rest by 48 h (the same as natural mating). The least amount of semen required to elicit ovulation is about 1.0 ml.[4]

Alpaca

In alpaca, follicles ovulate approximately 26 h after coital stimulation. Mounting accompanied by intromission is necessary to provide adequate stimulation for LH release and subsequent ovulation.[5] Deposition of semen, which contains ovulation-inducing factor (OIF),[6] has been shown to increase the chance of pregnancy. Prolonged copulation, causing abrasion and inflammation of the uterus, may enhance absorption of OIF.

References

  1. ↑ "Estrus". The University of Sydney. 2012. Retrieved September 12, 2014.
  2. ↑ Heape, W. (1905). "Ovulation and degeneration of ova in the rabbit.". Proc. R. Soc. B 76: 260–268. doi:10.1098/rspb.1905.0019.
  3. ↑ Staples, R.E. (1967). "Behavioural induction of ovulation in the oestrous rabbit.". J. Reprod. Fert. 13: 429–435. doi:10.1530/jrf.0.0130429.
  4. 1 2 Chen, B.X., Yuen, Z.X. and Pan, G.W. (1985). "Semen-induced ovulation in the bactrian camel (Camelus bactrianus).". J. Reprod. Fert. 74 (2): 335–339. doi:10.1530/jrf.0.0740335.
  5. ↑ Fernandez-Baca, S., Madden, D.H.L. and Novoa, C. (1970). "Effect of different mating stimuli on induction of ovulation in the alpaca.". J. Reprod. Fert. 22: 261–267. doi:10.1530/jrf.0.0220261.
  6. ↑ Adams, G.P., Ratto, M.H. (2012). "Ovulation-inducing factor in seminal plasma: A review". Animal Reproduction Science 136: 148–156. doi:10.1016/j.anireprosci.2012.10.004.
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