Effect of gonadotrophin releasing hormone on levels of luteinising hormone in cattle synchronised with dinoprost.

Synchronisation of oestrus was achieved in a group of three cows and two heifers with dinoprost. Sixty-six hours after the second injection of dinoprost, 0.125 mg synthetic gonadotrophin releasing hormone (GnRH) was given intramuscularly. Concentrations of luteinising hormone (LH) were monitored in peripheral blood and close grouping of preovulatory LH peaks was seen around 2.5 hours after injection of GnRH.