Use of GnRH to synchronize ovulation in holstein cows and heifers treated with GnRH and prostaglandin

Synchronisation of oestrus and reproductive performance of dairy cows following administration of oestradiol benzoate or gonadotrophin releasing hormone during a synchronised pro‐oestrus

“…1 Administration of PGF 2α induces luteolysis and the second injection of GnRH synchronises and induces ovulation. Ovulation rates following this protocol have been reported to be between 87 and 100% [3][4][5] but only 30% of cows are expected to show oestrus by or shortly after the second injection of GnRH. 6 Pregnancy rates following treatment and a single timed insemination at the synchronised ovulation in dairy cows have been variable with pregnancy rates in some studies reported to be equal to 2,7 or less than 8 control cows inseminated on detection of oestrus.…”

“…An alternative synchronisation program based on the use of an IVP 4 and ODB involves administration of ODB at the time of device insertion, PGF 2α at the time of device removal, 7 or 8 days later, and administration of ODB 24 h after removal of inserts. 9,10 Administration of ODB at the time of device insertion causes atresia of existing dominant follicles and synchronises the emergence of a new wave of ovarian follicles 4 to 5 days later.…”

“…No significant effects of BCS, age, calving to MSD intervals were found on the odds of cows being classified as phantom cows in the present study. Previously, associations between low BCS, 13 and anoestrous cows treated with an IVP 4 14 and increased odds of cows being classified as phantom cows have been reported. The number of cows in the present study may have been too low to provide adequate statistical power to detect associations between phantom cows and potential predisposing factors.…”

Effect of GnRH Dose on Occurrence of Short Oestrous Cycles and LH Response in Cyclic Dairy Heifers

“…Similarly in the Ovsynch oestrus synchronization protocol, the GnRH dose used is often 0.1 mg (Pursley et al. 1994; Silcox et al. 1995; Macmillan et al.…”

Oestrus Synchronization by PGF2α and GnRH in Intervals according to Stage of Follicular Development at Time of Initial Treatment in Cows

“…On the basis of these data we determined 3 phases of the follicular development according to diameters of ovarian follicles -growing phase (follicles 3-7 mm, Group 1), phase of early dominance (follicles 3-7 mm and 8-14 mm, Group 2) and phase of late dominance with preovulatory/preatretic follicles (follicles 4-7 mm, 8-14 mm and 15-23 mm, Group 3). Past research showed that growing dominant follicles (greater than 10 mm in diameter) usually ovulate after GnRH treatment (Prescot et al 1992;P u rsley et al 1995;Silcox et al 1995). But GnRH is effective only in the presence of functional dominant follicle during its growing and the 1st part of the static phase (Silcox et al 1993) when follicle granulosa cells content maximum number of LH receptors (X u et al 1995;Bodensteiner et al 1996b).…”