Effect of transient suppression of LH surge on superovulatory responses in Ongole cows

The aim of the present study was to evaluate the effect of temporary suppression of LH surge during superovulation on ovarian response, total and viable embryo recovery and number of freezable (grade 1) embryos. Ongole cows (12) were randomly divided into 2 equal groups. Both groups 1 (control) and 2 (LH suppression) cows, received a silastic auricular implant containing 3 mg norgestomet (NOR) along with a 2 ml i/m injection containing 3 mg NOR and 5 mg estradiol valerate, 4 days before the start of gonadotrophin treatment. Superovulation treatment involved administration of 200 mg NIH-FSH-P1 in a twice daily descending dose schedule for 4 days and induction of luteolysis at 48 h (PGF1) and 60 h (PGF2) after initiating gonadotrophin treatment. In group 1 cows the implant was removed 12 h after PGF1 whereas in group 2 it was removed at 60 h post PGF1. At the time of implant removal the latter group was administered 25 mg pLH. Non surgical embryo collection was performed about 7–7.5 days after the onset of superestrus. The recovered embryos were evaluated and graded based on their morphology. The mean ovarian response (mean CL) was significantly higher in group 2 compared to group 1 cows. Similarly the total and viable embryo recovery and grade 1 embryos, respectively, were higher, albeit nonsignificantly, in group 2 than in group 1 cows. The fertilization rate in group 2 was comparable to that of group 1 The time of occurrence of LH surge (h post PGF1) was significantly longer in group 2 donors compared to group 1. The study, therefore, revealed that temporary suppression of endogenous LH surge resulted in higher ovarian response, and it had no adverse impact on the fertilization rate, yield of viable as well as freezable embryos.