An investigation on the efficacy of Ov-synch and modified Ov-synch with single dose of PGF2 Alpha in combination with GnRH in Synchronization of estrus in HF x local cross bred cows was conducted in and around Mekelle, From November 2009 to May 2010. A total of 20 animals, non cyclic (presence of well developed CL in either ovary) were inducted in to the experiment. Based on clinical examination animals were divided in to two groups. Group I animals: in clued both types of cycling with a CL and non cycling with out CL and received an IM dose of 75micro gram GnRH on day 0, 25mg PGF2 Alpha on...