Efficacy of GnRH-PGf2alpha - GnRH in Synchronizing Estrus in Cross Bred Dairy Cows

Abstract

An investigation on the efficacy of Ov-synch and modified Ov-synch with single dose of PGF2_a in combination with GnRH in Synchronization of estrus in HF x local cross bred cows was conducted in and around Mekelle, From November 2013 to May 2014. 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 without CL and received an IM dose of 75mg GnRH on day 0, 25mg PGF_2a on day 7 followed by a second dose of 75mg GnRH on day 9, all the animals were given a single insemination 24hrs after the second GnRH administration. Group II animals: were all cycling animals with a well-developed CL in either ovary, received a simultaneous administration of 25mg PGF_2a IM and 100mg GnRH IM and give two fixed time insemination at 48 and 72 hrs after the treatment Five animals were excluded from the study due to various reasons. There for, a total 15 animals (8 cows and 7 heifers) were retained in the study and inseminated, Out of which 5 (33.3%) [3 cow (37.5%) and2 heifer (28.6%)] were diagnosed pregnant. The differences in conception rate of 28.6% and 37.5% in Group I and Group II respectively. The conception rates in the two treated groups were similar. The overall conception rates of 28.6 and 37.5% in the two groups were poor. For further confirmation of the results obtained in these protocols, another study; under controlled conditions of management and feeding is necessary before it can be recommended for wide spread application.

Keywords: Cattle, CL, GnRH, PGF_2a, Synchronization, AI, Pregnancy rate,