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15/1/03 Ovulation-inducing Factors in the Seminal Plasma of the Camel By Eshel Indich-Navon, 4th year student Mentor: Michael Van-Straten.
Camelids of the Old World (dromedary or one humped camel and bactrian or two humped camel) and the New World (e.g. llama and alpaca) are seasonal breeders, poly-oestrus animals and induced ovulators. Breeding season depends on lengthening of daylight and low temperatures and it changes geographically. In Israel the rutting season of the male is around October to April but for the females the breeding season is all year around. For other induced ovulators like the rabbit and the cat the mechanism, which induces ovulation, is already well documented. For the Camelids this mechanism is still not fully understood. It is suggested that copulation, coital stimuli, neurohormonal responses to mechanical stimuli and some factors in the seminal plasma contribute to the ovulatory response. Ovulation can also be induced artificially by the treatment of GnRH or hCG.
Chen et al (1983) reported that vaginal insemination induced ovulation in the bactrian camel. In 1985 they also demonstrated that ovulation is induced by the insemination of seminal plasma which was separated from the spermatozoa. However, in dromedaries, intrauterine injection of whole semen or seminal plasma failed to induce ovulation (Musa and Abusineina 1978; Sheldrick et al 1992). Xu et al (1985) investigated the hormone concentration before and after semen induced ovulation and found that the LH peak after insemination appeared only after 4 h compared to 15 min in the rabbit suggesting that the rise of LH in the camel is evoked by humoral pathway whilst in the rabbit it is known to be neural.
In two recent studies (Zhao et al; 2001 and Pan et al; 2001) a GnRH-like factor was isolated and purified from the seminal plasma of the bactrian camel. This factor is different from the native LHRH, LH, HCG, PMSG and PGF-2α by its amino-acid component and thus makes it a novel ovulation hormone in the bactrian camel not reported in other mammals.
References: Xu YS, Wang HY, Zeng GQ, Jiang GT, Gao YH, 1985: Hormone concentrations before and after semen-induced ovulation in the Bactrian camel (Camelus bactrianus). J Reprod. Fert. 74, 341-346.
Zhao XX, Li XL, Chen BX, 2001: Isolation of ovulation-inducing factors in the seminal plasma of bactrian camel by DEAD-cellulose chromatography.Reprod. Dom. Anim. 36, 177-181.
McKinnon AO, Tinson AH, Nation G,1994: Embryo transfer in dromedary camels. Theriogenology. 41, 145-150.
Bravo PW, Skidmore JA, Zhao XX, 2000: Reproductive aspects and storage of semen in Camalidae. Anim. Reprod. Sci. 62, 173-193.
Skidmore JA, Billah M, Allen WR, 1996: The ovarian follicular wave pattern and induction of ovulation in the mated and non-mated one-humped camel (Camelus dromedarius). J. Reprod. Fer. 106, 185-192.
Chen BX, Yuen ZX, Pan GW, 1985: Semen-induced ovulation in the bactrian camel (Camelus bactrianus). J. Reprod. Fer. 73, 335-339.
Marie M, Anouassi A, 1987: Induction of luteal activity and progesterone secretion in the nonpregnent one-humped camel (Camelus dromedaries). J. Reprod. Fer. 80, 183- 192.
Pan G, Chen Z, Liu X, Li D, Xie Q, Ling F, Fang L, 2001: Isolation and purification of the ovulation-inducing factor from seminal plasma in the bactrian camel (Camelus bactrianus). Theriogenology. 55, 1863-1879.
Xu YS, Wang HY, Zeng GQ, Jiang GT, Gao YH, 1985: Hormone concentration before and after semen-induced ovulation in the bactrian camel (Camelus bactrianus). J. Reprod. Fer. 74, 341-346.
Al Eknah MM, 2000: Reproduction in Old World camels. Anim. Reprod. Sci. 60-61, 583-592.
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