PREOVULATORY CHANGES AND OVULATION IN CATTLE UNDERGOING SPONTANEOUS OR CLOPROSTENOL-INDUCED LUTEOLYSIS
AbstractThe follicular population, diameter of the ovulatory and subordinate follicles, corpus luteum (CL) size, concentration of progesterone and estradiol-17p were studied following spontaneous or cloprostenol-induced luteolysis. A total of 14 heifers received cloprostenol treatment on Day 9-11 of the cycle to synchronize their estrus. Subsequently, they were divided into two groups, one group which was allowed to undergo spontaneous luteolysis and the other group in which estrus was induced from days 9 to 12. In the induced-group, transrectal ultrasonography were performed daily started two days prior to injection until the onset of estrus. In the spontaneous-group, ultrasonography was done daily from day 15 until the onset of estrus. In both groups scanning were performed every 4 h from the onset of estrus until ovulation was ascertained. Small (SF, 2-4 mm), medium (MF.5-9 mm ) and large (LF,>9mm) size follicles were recorded. The diameter of largest and subordinate follicles were measured and blood were drawn from jugular vein at approximately around scanning and the plasma were used for measurement of progesterone (P4) and estradiol-17p (E2) concentration. There was no different in term of number of SF, MF and LF (P>0.05) between the two groups. Similarly, no effect of side (left vs. right ovary) and CL position (ipsi- vs contralateral to the ovary) was found (P>0.05). However, it was demonstrated that mean number of ovulatory follicles was higher (PO.01) in the spontaneously ovulating group while the regressing-CL size was larger in the cloprostenol induced animals (P<0.05). Occurrence of time of ovulation in relation to initial signs of estrus was observed in both groups of animals. This variation could be attributed to the existence of a large preovulatory follicle which enhanced the time ovulation. Conversely, when subordinate follicles showed grow up and replace the large follicle the interval from heat to ovulation was prolonged. Progesterone experienced a more steep decrease than the spontaneous group of animals and a positive correlation was observed between the diameter of CL and the P4 concentration. For E2 there was a positive correlation between the E2 and follicular size. It is concluded that the variation in follicular among animals contributed to the variability in timing of ovulation, particularly prostaglandin-induced animals. The diameter of ovulatory follicle in spontaneous group was larger as compared to induced-group.Key words : follicular development, ovulation, cloprostenol,cattle reproduction
LicenseAuthors who publish with this journal agree with the following terms:
- Authors retain copyright and grant the journal right of first publication, with the work 1 year after publication simultaneously licensed under a Creative Commons attribution-noncommerical-noderivatesÂ 4.0 InternationalÂ License that allows others to share, copy and redistribute the work in any medium or format,Â but only where the use is for non-commercial purposesÂ and an acknowledgement of the work's authorship and initial publication in this journal is mentioned.
- Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.
- Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work (See The Effect of Open Access).