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Nature, Effects and Possible Mechanisms of Action of Ovulation Inducing Factor: A Review

Shabir Ahmad Lone Nadeem Shah Ajeet Singh Puneeth Kumar D.S.
Vol 7(4), 59-67

In Bactrian camels, the seminal plasmas ovulation inducing effect was reported around 30 years ago and the substance responsible was termed as ovulation-inducing factor (OIF). Studies have confirmed that in llamas and alpacas based on biological and chemical properties, OIF was identified as βNGF. OIF is a highly conserved protein and studies have revealed that presence and function of seminal OIF are conserved among species that are considered to be induced ovulators as well as those of spontaneous ovulators. Abundant amounts of OIF/NGF in seminal plasma and seminal plasma effects on ovarian function support the endocrine mode of action. The present review focuses on nature, effects and possible mechanisms of action of OIF/NGF.

Keywords : Copulation Seminal Plasma Spontaneous Ovulators Induced Ovulators OIF


Based on the type of stimulus responsible for eliciting GnRH release from the hypothalamus, mammals are classified into spontaneous or induced ovulators. In induced ovulators such as rabbit, bactrian camel, llama, alpaca, cat and ferret, copulation elicits neural signals responsible for triggering hypothalamic GnRH secretion, which leads to preovulatory discharge of LH from the pituitary (Bakker and Baum 2000). The presence of an elaborate accessory gland system in male species and induction of ovulation in females are two most intriguing mysteries in the field of biology of reproduction. Traditionally, these two processes have been thought as simply vestiges of primitive lineages (Bedford 2004; Kauffman and Rissman 2005), but current literature available about the presence of ovulation-inducing factor (OIF) in seminal plasma may provide some knowledge that links these processes together. Induction of ovulation by copulation was discovered more than 100 years ago by Walter Heape, who discovered doe rabbit permits coitus during oestrus, and withholding male at that time leads to degeneration of ova in the ovary; they are not released from the ovary (Heape 1905). In South American camels, induced ovulation phenomenon was reported in the late 1960s (England et al., 1969; San Martin et al., 1968) and about a decade later in bactrian and dromedary camels (Chen and Yuen 1979). Previous literature yielded that in >95% of females, ovulation occurs after mounting and intromission and only <14% in absence of later (Fernandez-Baca et al., 1970). Thus during copulation, physical stimulation of genitalia is primarily involved in ovulation in case of induced ovulators. Contrary to these, some previous studies in Bactrian camels revealed that some agent present in the semen was responsible for eliciting ovulation in Bactrian camels, rather than the copulation induced mechanical stimulation. The administration of Bactrian camel seminal plasma intravaginal (Chen et al., 1985; Xu et al., 1985), intramuscular or intrauterine lead to induction of ovulation in female Bactrian camels. An injection of a single intramuscular dose of seminal plasma in females of llamas and alpacas resulted ovulation in >90% females (Adams et al., 2005).

Nature of OIF

Due to LH-releasing effects (Paolicchi et al., 1999) and GnRH immuno-reactivity in seminal plasma of humans (Sokol et al., 1985) lead to the supposition that OIF may be related to the GnRH. Results documented that OIF is not a steroid, prostaglandin or GnRH rather it is a protein which is resistant to heat and enzymatic digestion with proteinase K and has a molecular mass of approximately of 30 kDa (Ratto et al., 2010). Data from X-ray diffraction revealed that OIF was similar to beta-nerve growth factor (ß-NGF) and it was revealed that biological activity of OIF was similar to NGF (Adams et al., 2016). Purified OIF from llama’s seminal plasma is a highly conserved protein ß-NGF (Ratto et al., 2012). In the seminal plasma of alpacas, ß-NGF is a protein that is expressed majorly and is involved in inducing ovulation (Kershaw-Young et al.,2012). As revealed from previous purification experiments, seminal plasma of bull is a rich source of that bovine seminal plasma NGF (Harper et al., 1982) and is likely to be produced by seminal vesicles (Hofmann and Unsicker 1982). It has also been reported in the prostate gland of bulls, rabbits and guinea pigs (Harper et al., 1979, 1982).

Effects of OIF / NGF

LH Release and Ovulation

In alpacas and llamas, injecting seminal plasma intramuscularly (equivalent to one-fourth to half of an ejaculate) resulted ovulation in 33 of 35 (94%) females as compared to 0 of 35 (0%) with saline (Ratto et al., 2005) and LH surge timing was similar to that reported after natural mating (Bravo et al., 1990). LH surge duration was prolonged after treatment with seminal plasma as compared to GnRH treatment (Adams et al., 2005). Ovulations were detected 29.3±0.7 hr after treatment with seminal plasma as revealed by ultrasonographic examination every 4 hr (Adams et al., 2005), which were similar to interval after natural mating or treatment with GnRH or LH (Ratto et al., 2006). Transcervical intrauterine deposition of seminal plasma in alpacas did not resulted in ovulation. These differences may be due to reduced absorption of OIF from the genital mucosa than intramuscular administration (Adams et al., 2005). Camelids have copulation time of 30–50 min (Bravo et al., 1990) and semen is deposited uterus, normally due to copulation, there is acute, transient inflammation of endometrium resulting from repeated abrasions by the penis (Bravo et al., 1996). In alpaca’s intrauterine treatment with endometrial curettage and twice dose of seminal plasma revealed that 41% females ovulated without curettage treatment and 67% ovulated in the curettage group (Ratto et al., 2005). Seminal plasma is more effective when given through intramuscular route as compared to intrauterine and in case of rabbits GnRH dose needed for ovulation was 10 to 20 times higher when given intravaginally than intramuscularly (Rebollar et al., 2012). It is the degree of absorption of a seminal factor from the genital mucosa into circulation (i.e. systemic dose) and not the response of tubular genitalia to physical stimulation that is responsible for ovulation (Adams et al., 2016). Seminal plasma has been used for induction of ovulation in llamas, in absence of copulation and copulation alone cannot result in ovulation without the presence of seminal plasma (Berland et al., 2016).

Dose Related Effects of OIF/NGF on Ovulatory Responses

Studies have revealed that OIF has a dose-related effect on the ovulatory mechanism and this effect is pronounced at various physiologically relevant doses, which may be as little as 1/100th that present in an ejaculate. It has also been observed that dose of OIF required to elicit pituitary and ovarian responses was higher when administered by intrauterine infusion than by intramuscular or intravenous routes (Silva et al., 2015). Surge in plasma LH levels and rates of ovulation were similar in female llamas that were injected with 2 mg OIF intramuscularly or intravenously, however, those treated by intrauterine deposition did not resulted in LH response and ovulations. But when intrauterine dose was increased to the total amount present in an average llama ejaculate (i.e. 5 ml seminal plasma or 20 mg of OIF), resulted a surge in LH concentration as compared to that yielded with lower intramuscular or intravenous dose (Adams et al., 2016).

Luteotrophic Effect of OIF/NGF

A functional corpus luteum (CL) is indispensible for maintenance of pregnancy) throughout gestation in camelids (Al-Eknah et al., 2001). In llamas, maintenance of functional CL between 8 and 10 days after ovulation has been implicated in maternal recognition of pregnancy (Adams et al., 1991), and early luteogenic processes may be associated with the ability of CL to respond early pregnancy signals. It has been seen that CL was larger in female llamas that were treated intramuscularly with a conservative dose of homologous seminal plasma; moreover CL regressed later and produced more than two times progesterone than CL resulting from GnRH-induced ovulation luteotrophic effect may be attributed to elicitation of LH secretion pattern by seminal plasma. Seminal plasma induced LH surge was sustained beyond the 8-hr sampling period in animals treated with OIF and after GnRH treatment; concentrations of LH were basal by 6 hr. The surge in plasma LH concentration triggered by seminal plasma was sustained beyond the 8-hr sampling period in OIF-treated animals, whereas LH concentrations were basal by 6 hr after GnRH treatment (Adams et al., 2016). Angiogenesis plays a pivotal role during the formation of CL, due to the fact that CL receives highest blood supply per unit of tissue than any other organ of the body (Wiltbank et al., 1988).

OIF/NGF treated llamas had greater blood flow to the pre-ovulatory follicle 4 hr post treatment as compared to GnRH treated ones. In addition to this OIF/NGF treated llamas had also higher vascular flow to the CL and greater concentrations of plasma progesterone 6 days after treatment (Adams et al., 2016). Giving two doses of OIF/ NGF, given just before and at the time of ovulation resulted in development of larger CL with greater vascularization and also produced higher progesterone concentrations as compared to single pre-ovulatory dose induced CL (Fernandez et al., 2014). In cattle (a spontaneous ovulator), both camelid and bovine seminal plasma were found to be luteotrophic, although, no measurable increase in LH concentrations in plasma were detected (Tribulo et al., 2015). Recent findings in cattle revealed that OIF/NGF induced luteotrophic effect is mediated by directly at the level of the ovary via interaction with trkA receptors of theca and granulosa cells of developing CL and dominant follicle (Carrasco et al., 2016). NGF may be an important mediator of ovulation due to seminal plasma in llamas due to the fact that ovulation does not take place if blood βNGF levels do not increase. This increase in blood βNGF levels occurs after copulation with an intact male or intrauterine infusion of seminal plasma (Berland et al., 2016).

Possible Mechanisms of Action

Although it is clear that seminal OIF/NGF responsible for ovulation mediates the effect on through surge release of LH into circulation, however it is not clear whether site of action of OIF is primarily at the site of hypothalamus or also involves the pituitary gland. Study revealed that GnRH antagonist (cetrorelix) pretreatment of llamas resulted in blockade of LH release and ovulation, which suggest a direct or indirect effect of OIF on GnRH releasing neurons in hypothalamus (Silva et al., 2011). In ovariectomized llamas, response of LH to OIF/NGF treatment was muted and after pre-treatment with oestradiol resulted in partial restoration of LH response, in agreement with the hypothesis that hypothalamus is involved in the pathway of OIF/NGF (Adams et al., 2016). Numerous in vitro studies documented that effect of OIF/NGF on pituitary gonadotrophs is direct. An induced release of LH secretion was reported following treatment of primary cultures of llama and bovine anterior pituitary cells and the magnitude of LH release was proportional to treatment dose (Bogle et al., 2012). Purified OIF or seminal plasma from Bactrian camels or alpacas addition to primary culture of rat pituitary cells caused the secretion of LH (Zhao et al., 2001). Binding with specific (trkA) and non-specific (p75) receptors is involved in effect of OIF/NGF on the hypothalamo-pituitary-ovarian axis. In induced ovulators, neural pathways involved in the activation of GnRH neurons are not well understood. Initial studies of the pattern of distribution revealed that around 60% of GnRH neurons were located in the anterior and medio-basal hypothalamus and were scattered widely rather than in focal accumulations or nuclei (Carrasco 2016). OIF/NGF molecule with over 100 amino acids and molecular mass of 26 kDa, is so big that it cannot diffuse through the blood–brain barrier (Banks 2009) and hence needs an active transport mechanism. In rats, NGF receptors have been found within the hypothalamus (Gibbs and Plaff 1994). It has been observed that elicitation of the LH surge using exogenous OIF/NGF begins and peaks 1-2 hr after that elicitation by exogenous GnRH (Adams et al., 2016). The delayed response with OIF/NGF may be due to an intermediate step in the pathway needed for release of GnRH/LH. The LH surge magnitude was dose-dependent following treatment with the two peptides (Silva et al., 2012; Tanco et al., 2011). Some other possible pathways reveal direct action on terminals of GnRH neurons or a direct action on pituitary gonadotrophs. In 75% of LH-containing gonadotroph cells and 44% of those cells with high-affinity NGF receptor trkA in anterior pituitary cells of rat (Patterson and Childs 1994). Some school of thought suggests β1 tanycytes are involved in pulsatile release of GnRH into the portal blood (Rodriguez et al., 2005). In the lateral regions of the median eminence, GnRH nerve fibres and their endings are concentrated and separate from the perivascular space by unique cells called tanycytes, which line the floor of third ventricle (Rodriguez et al., 1979). Within the median eminence, OIF/NGF stimulates the release of molecules that regulate the transient and cyclic release at the GnRH terminals (Prevot, 2002). Another hypothesis is that organum vasculosum of the lamina terminalis (OVLT) outside of the blood-brain barrier may be involved in sensing the travelling molecules in the systemic blood (Herde et al., 2011; Rodriguez et al.,2010).

OIF/ NGF in the Male

NGF was initially reported from prostate gland of guinea pig (Harper et al., 1979); later on research was carried out to explore the source and abundance of NGF in the male accessory glands of other species. Among the prostate glands of the guinea pig, the rabbit and bull, the highest concentrations of NGF were found to be contained in prostates of guinea pig. Recent researches have revealed that at least one male accessory gland in all species contains OIF/NGF (Bogle 2016). Prostate gland appears to be main source of OIF/NGF in llamas, rabbits, guinea pigs and white-tailed deer and ampullae and seminal vesicles in cattle and bison. On the basis of response to in vivo bioassay (ovulation), in vitro bioassay (PC12 cells) and immunoassay (ELISA, RIA, immuno-histochemistry; Bogle 2016; Tribulo et al., 2015; Maranesi et al., 2015; Casares-Crespo et al., 2016), highest levels of OIF/NGF appears to be in camelids and rabbits. In llamas, 90-100% of ovulation rate was reported on treatment with seminal plasma of camelid or rabbit (Adams et al., 2005; Silva et al., 2011) and ovulation rates were 26% with bull semen (Ratto et al., 2006), and 18%, 29% using stallion and boar semen, respectively (Bogle et al., 2011). When compared to llama seminal plasma, concentration of OIF/NGF in bovine seminal plasma was only 10 to 20% and female llamas treated with bovine seminal plasma, with a dose of OIF/NGF equivalent to that found in llama seminal plasma yielded ovulation rates similar to that an equal dose of OIF/NGF induced by llama seminal plasma (Tribulo et al., 2015).


The ovulation inducing effect of seminal plasma in camels is reported to be due to presence of protein known as OIF, was identified as βNGF. In reproductive tract, the presence and function of an OIF/NGF system has been reported in many species of animals including various spontaneous and induced ovulators. Seminal plasma effects on ovarian function and presence of abundant OIF/NGF in it, supports endocrine mode of action of OIF. Ovulation is brought about by LH surge in the llamas and alpacas, and it is the function of the degree of absorption of a seminal factor from the genital mucosa into circulation. The magnitude of LH releases (central mechanism) and changes in the expression of specific receptors in ovarian follicles (local mechanism) may be responsible for luteotrophic effect of OIF/NGF. Seminal plasma of camels and rabbits has highest levels of OIF/NGF but has been identified in at least one of the male accessory glands in all species. Further studies are needed to determine the prevalence and function of OIF among various species and to test some unexplained causes of infertility which may be based on alterations in levels of OIF.


  1. Adams GP, Ratto, MH, Silva ME and Carrasco RA. 2016. Ovulation-inducing factor (OIF/NGF) in seminal plasma: a review and update. Reproduction in Domestic Animal.51(2): 4-17.
  2. Adams GP, Ratto MH, Huanca W and Singh J. 2005. Ovulation-inducing factor in the seminal plasma of alpacas and llamas. Biology of Reproduction. 73: 452–457.
  3. Adams GP, Sumar J and Ginther OJ. 1991. Form and function of the corpus luteum in llamas. Animal Reproduction Science. 24: 127–138.
  4. Al-Eknah MM, Homeida AM, Ramadan RO, Al-Modhi FA and Al-Busadah KA. 2001. Pregnancy dependence on ovarian progesterone in the camel (Camelus dromedaries). Emirates Journal of Agriculture Science. 13: 27–32.
  5. Bakker J and Baum MJ. 2000. Neuroendocrine regulation of GnRH release in induced ovulators.  Front Neuroendocrinology. 21: 220–262.
  6. Banks WA. 2009. Characteristics of compounds that cross the blood brain barrier. BMC Neurology, 9 (Suppl 1), S3.
  7. Bedford JM. 2004. Enigmas of mammalian gamete form and function. Biological Reviews. 79: 429–460.
  8. Berland MA, Ulloa-Leal C, Barría M, Wright H, Dissen GA, Silva ME, Ojeda SR and Ratto MH. 2016. Seminal Plasma Induces Ovulation in Llamas in the Absence of a Copulatory Stimulus: Role of Nerve Growth Factor as an Ovulation-Inducing Factor. Endocrinology. 157 (8): 3224-3232.
  9. Bogle OA. 2016. Nerve growth factor: Its role in male fertility as an ovulation inducer. PhD Thesis, University of Saskatchewan, pp 182.
  10. Bogle OA, Ratto MH and Adams GP. 2011. Evidence for the conservation of biological activity of ovulation-inducing factor (OIF) in seminal plasma. Reproduction. 142: 277–283.
  11. Bogle OA, Ratto MH and Adams GP. 2012. Ovulation-inducing factor (OIF) induces LH secretion from pituitary cells. Animal Reproduction Science. 133: 117–122.
  12. Bravo PW, Fowler ME, Stabenfeldt GH and Lasley BL. 1990. Endocrine responses in the llama to copulation. Theriogenology. 33: 891–899.
  13. Bravo WP, Bazab PJ, Troedsson MHT, Villalta PR and Garnica JP. 1996. Induction of parturition in alpacas and subsequent survival of neonates. Journal of the American Veterinary Medical Association. 209: 1760–1762.
  14. Carrasco R. 2016. Ovulation-inducing factor/nerve growth factor (OIF/ NGF): Immunohistochemical studies of the bovine ovary and the llama hypothalamus. Master’s Thesis, University of Saskatchewan, pp 95.
  15. Carrasco R, Singh J and Adams GP. 2016. The dynamics of trkA expression in the bovine ovary are associated with a luteotrophic effect of ovulation inducing factor/nerve growth factor (OIF/NGF). Reproductive Biology and Endocrinology (submitted, May 2016).
  16. Casares-Crespo L, Talaván AM and Viudes-de-Castro MP. 2016. Can the genetic origin affect rabbit seminal plasma protein profile along the year? Reproduction in Domestic Animals 51: 294–300.
  17. Chen BX and Yuen ZX. 1979. Reproductive pattern of the Bactrian camel. In W. R. Cochrill (Ed.), The camelid: An all-purpose animal (pp. 364–386). Uppsala, Sweden: Scandinavian Institute of African Studies.
  18. Chen BX, Yuen ZX and Pan GW. 1985. Semen-induced ovulation in the Bactrian camel (Camelus bactrianus). Journal of Reproduction and Fertility. 73: 335–339.
  19. England BG, Foote WC, Mathewes DH, Cordozo AG and Riera S. 1969. Ovulation and corpus luteum function in the llama (Lamaglama). Journal of Endocrinology. 45: 505–513.
  20. Fernandez A, Ulloa-Leal C, Silva M, Norambuena C, Adams GP, Guerra M and Ratto MH. 2014. 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. Animal Reproduction Science. 149: 345–352.
  21. Fernandez-Baca S, Madden DHL and Novoa C. 1970. Effect of different mating stimuli on induction of ovulation in the alpaca. Journal of Reproduction and Fertility. 22: 261–267.
  22. Gibbs RB and Plaff DW. 1994. In situ hybridization detection of trka mRNA in brain: Distribution, colocalization with p75NGFR and up-regulation by nerve growth factor. Journal of Comparative Neurology. 341: 324–339.
  23. Harper GP, Barde YA, Burnstock G, Carstairs JR, Dennison ME, Suda K and Vernon CA.1979. Guinea pig prostate is a rich source of nerve growth factor. Nature. 279: 160–162.
  24. Harper GP, Glanville RW and Thoenen H. 1982. The purification of nerve growth factor from bovine seminal plasma: Biochemical characterization and partial amino acid sequence. Journal of Biological Chemistry. 257: 8541–8548.
  25. Heape W. 1905. Ovulation and degeneration of ova in the rabbit. Proceedings of the Royal Society. B76: 260–268.
  26. Herde MK, Geist K, Campbel RE and Herbison AE. 2011. Gonadotropin-Releasing hormone neurons extend complex highly branched dendritic tress outside the Blood-brain barrier. Endocrinology. 152: 3832–3841.
  27. Hofmann HD and Unsicker K. 1982. The seminal vesicle of the bull: A new and very rich source of nerve growth factor. European Journal of Biochemistry. 128: 421–426.
  28. Kauffman AS and Rissman EF. 2005. Neuroendocrine control of mating-induced ovulation.
  29. In The physiology of reproduction. E. Knobil and JD Neill (Eds.) (pp. 2283–2326). St Louis, Missouri: Elsevier.
  30. Kershaw-Young CM, Druart X, Vaughan J and Maxwell WM. 2012. β-Nerve growth factor is a major component of alpaca seminal plasma and induces ovulation in female alpacas. Reproduction, Fertility, and Development. 24: 1093–1097.
  31. Maranesi M, Zerani M, Leonardi L, Pistilli A, Arruda-Alencar J, Stabile AM, Rende M, Castellini C, Petrucci L, Parillo F, Moura A and Boiti C. 2015. Gene expression and localization of NGF and its cognate receptors NTRK1 and NGFR in the sex organs of male rabbits. Reproduction in Domestic Animals 50: 918–925.
  32. Paolicchi F, Urquieta B, Del Valle L and Bustos-Obregon E. 1999. Biological activity of the seminal plasma of alpacas: Stimulus for the production of LH by pituitary cells. Animal Reproduction Science. 54: 203–210.
  33. Patterson JC and Childs GV. 1994. Nerve growth factor and its receptor in the anterior pituitary. Endocrinology 35: 1689–1696.
  34. Prevot V. 2002. Glial-neuronal- interactions are involved in the control of GnRH secretion. Neuroendocrinology. 14: 247–255.
  35. Ratto MH, Huanca W and Adams GP. 2010. Ovulation-inducing factor: A protein component of llama seminal plasma. Reproductive Biology and Endocrinology. 8: 44.
  36. Ratto MH, Huanca W, Singh J and Adams GP. 2005. Local versus systemic effect of ovulation-inducing factor in seminal plasma of alpacas. Reproductive Biology and Endocrinology. 3: 29.
  37. Ratto MH, Huanca W, Singh J and Adams GP. 2006. Comparison of the effect of natural mating, LH, and GnRH on interval to ovulation and luteal function in llamas. Animal Reproduction Science 91: 299–306.
  38. Ratto MH, Huanca W, Singh J and Adams GP. 2006. Comparison of the effect of ovulation-inducing factor (OIF) in the seminal plasma of llamas, alpacas, and bulls. Theriogenology. 66: 1102–1106.
  39. Ratto MH, Leduc YA, Valderrama XP, van Straaten KE, Delbaere LTJ, Pierson RA and Adams GP. 2012. The nerve of ovulation-inducing factor in semen. Proceedings of the National Academy of Sciences. 109: 15042–15047.
  40. Rebollar PG, Dal Bosco A, Millán P, Cardinali R, Brecchia G, Sylla L, Lorenzo PL and Castellini C. 2012. Ovulating induction methods in rabbit does: The pituitary and ovarian responses. Theriogenology. 77: 292–298.
  41. Rodriguez EM, Blazquez JL and Guerra M. 2010. The design of barriers in the hypothalamus allows the median eminence and the arcuate nucleus to enjoy private milieus: The former opens to the portal blood and the latter to the cerebrospinal fluid. Peptides. 31: 757–776.
  42. Rodriguez EM, Blazquez JL, Pastor FE, Pelaez B, Penia P, Peruzzo B and Amat P. 2005. Hypothalamic tanycytes; a key component of brain-endocrine interaction. International Review of Cytology. 247: 89–164.
  43. Rodriguez EM, Gonzalez CB and Delannoy L. 1979. Cellular organization of the lateral and post infundibular regions of the median eminence in the rat. Cell and Tissue Research. 3: 377–408.
  44. Silva ME, Colazo MG and Ratto MH. 2012. GnRH dose reduction decreases pituitary LH release and ovulatory response but does not affect CL development and function in llamas. Theriogenology 77: 1802–1810.
  45. Silva ME, Fernández A, Ulloa-Leal C, Adams GP and Ratto MH. 2015. LH release and ovulatory response after intramuscular, intravenous, and intrauterine administration of beta-nerve growth factor of seminal plasma origin in female llamas. Theriogenology. 84: 1096–1102.
  46. Silva ME, Niño A, Guerra M, Letelier C, Valderrama XP, Adams GP and Ratto MH. 2011. Is an ovulation-inducing factor (OIF) present in the seminal plasma of rabbits? Animal Reproduction Science. 127: 213–221.
  47. Sokol RZ, Peterson M, Heber D and Swerdlof RS. 1985. Identification and partial characterization of gonadotropin-releasing hormone-like factors in human seminal plasma. Biology of Reproduction. 33: 370–374.
  48. Tanco VM, Ratto MH, Lazzarotto M. and Adams GP. 2011. Dose response of female llamas to ovulation-inducing factor (OIF) from seminal plasma. Biology of Reproduction. 85: 452–456.
  49. Tribulo P, Bogle O, Mapletoft RJ and Adams GP. 2015. Bioactivity of ovulation inducing factor/nerve growth factor (OIF/NGF) in bovine seminal plasma and its effects on ovarian function in cattle. Theriogenology. 83: 1394–1401.
  50. Wiltbank MC, Dysko RC, Gallagher KP and Keyes PL. 1988. Relationship between blood flow and steroidogenesis in the rabbit corpus luteum. Journal of Reproduction and Fertility. 84: 513–520.
  51. Xu YS, Wang HY, Zeng GQ, Jiang GT and Gao HY. 1985. Hormone concentrations before and after semen-induced ovulation in the Bactrian camel (Camelus bactrianus). Journal of Reproduction and Fertility. 74: 341–346.
  52. Zhao XX, Li XL and Chen BX. 2001. Isolation of ovulation-inducing factors in the seminal plasma of Bactrian camels (Camelus bactrianus) by DEAE-cellulose chromatography. Reproduction in Domestic Animals. 36: 177–1781.
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