IntroductIonH ypothalamuses canpulsatile release the GnRH into the hypophyseal portal system with subsequent release of LH from the anterior pituitary into systemic circulation for inducing ovulation in mammals. The broad classification of species as either spontaneous or induced ovulators is based on the type of stimulus responsible for eliciting GnRH release from the hypothalamus (Adam et al., 2005). In spontaneously ovulating species (such as human, sheep, cattle, horse and pigs), the releasing of GnRH from the hypothalamus is triggered in the absence of progesterone and systemic estradiol concentrations exceed a threshold. In the induced ovulators (such as rabbits, ferrets, cats and camelids) the releasing of GnRH is contingent upon copulatory stimuli; hence, the ovulation is not a regular cyclic event (Bakker and Baum, 2000; Adam et al., 2005). Since a classic 1970 Peruvian study, dogma has maintained that physical stimulation of the genitalia during copulation is the primary trigger for inducing ovulation in alpacas and llamas. It is inaccurate to apply the term "oestrous cycle" in camels due to the pattern of ovulation in these animals,in contrast in spontaneous ovulators such as the cow and the mare (Bravo et al., 1990;Bravo et al., 1991).Camels are seasonally polyestrous animals with estrous cycle differed from that in other farm animals. The estrous cycle in camel is characterized by three phases lasting 24-28 days with absence of the luteal phase. These phases are including follicular growth, existence of mature follicles (estrous period) and follicular atresia. The estrous period is longer up to 8 days (Shalash, 1980;Shalash, 1987;Skidmore et al., 1996;Skidmore et al., 2009).Ovulation in the camel as in cat and rabbit occurs normally after the coitus. In these animals the neuroendocrine reflex involving the initiation of luteinising hormone release is delayed until coitus occurs . Manual stimulation of the cervix for 15 minutes in the camel did not induce ovulation but cause only partial luteinisation of the Graafian follicle, ovulation occurs 32 to 40 hours after copulation under the influence of luteinising hormone (LH) (Musa & Abu Sineina, 1978b;Wilson, 1984;Yagil, 1985). OvulatiOn induced FactOr (OiF): discOvery research ArticleAbstract | The seminal plasma consists of several components that stimulate the ovulation process. The great quantity of an ovulation-inducing factor (OIF) in seminal plasma has wide implication questions about identification, sources, mechanism of action, role among species and clinical applications in the infertility. The purpose of the current review is to focus on the current understanding of physiological and biochemical properties of seminal plasma in camelids. llamas and alpaca seminal plasma was used as agent of induced and spontaneous ovulators. Column chromatography was used to identify the ovulation-inducing factor as part of seminal plasma that stimulating hormone secretion (LH) and ovulation in llamas. OIF is β-NGF that is highly conserved. An endocrine rout...