It has been proposed that a neural pathway from the reproductive tract of ovine females to the pituitary gland exist, and a neural blocking agent, chloropromazine, has blocked ovulation in ewes
22. Randel et al.
11 has proposed that such a neural pathway also exists in cattle. Clitoral stimulation hastens the onset of ovulation, and stimulation of cervix reduces the time from the beginning of estrous to the occurance of LH surge in beef cattle
2.
Naturally mated sows have higher concentrations of plasma LH immediately after mating2. Tilton et al.23 have observed that natural mating has a temporary stimulatory effect on plasma LH concentrations approximately 1 h after copulation. In a study made by Zalesky et al.18 has noted that the presence of and mating with a bull did not affect the release of LH in cows. Kirsch et al.20 also observed that stimulation of the pelvic region during either natural mating or AI did not enhance release of LH. Cooper and Foote14 reported that the effect of clitoral stimulation on LH release was negative.
In the present study, it was observed that cauterization of clitoris did not affect LH concentration. LH levels were not significantly different between groups. This finding indicates that cauterization of clitoris did not affect pituitary release of LH. While these results are similar with the results of Zalesky et al.18 and Kirsch et al.20, they are inconsistent with the results reported by other authors2,6,10,11,24. The levels of serum LH detected in this study are within the range of plasma levels reported by Walters and Schallenberger25, whereas these findings are different from the finding reported by other researchers11,<24>,26.
Randel et al.11, reported that the time from estrous to ovulation was shortened to 4.3 hours in clitoral stimulated group than control group in cows. They claimed that the reason of shortening of this term is hastening of LH surge in the cow. Panth et al.27 and Singh et al.9 observed that clitoral stimulation increased pregnancy rate presumably by hastening LH surge. Ziecik et al.28 observed that mating can modulate the preovulatory surge of LH in gilts by prolonging the duration of LH release rather than by increasing plasma concentrations.
In the present study, cauterization of the clitoris did not affect the rate of LH secretion during preovulatory LH surge. Concentration of LH and duration of the preovulatory LH surge reported in the present study are similar to those reported25 for cows not exposed to any type of stimuli, and are comparable to those reported by other researchers9,11,18,27,28.
In conclusion, clitoral cauterization applied under epidural anaesthesia in healthy cows did not affect the mean LH concentration, LH peak concentration, the time from the beginning of estrous to onset of LH surge, to end of LH surge and to LH peak, mean duration of LH surge.
Acknowledgments
We would like to thank TUBITAK (Turkish Scientific and Techonological Research Council) for generous funding.