SRINIVAS, M (Major)MOULI KRISHNA, KSREEDEVI, BRAMALAKSHMI, N2016-12-152016-12-152015-11http://krishikosh.egranth.ac.in/handle/1/90360ABSTRACT: The present Research work was undertaken by utilizing 24 postpartum acyclic crossbred cows maintained under diverse (village) managemental conditions. The work was designed to study the efficacy of different synchronization protocols viz., Ovsynch (Group I), Ovsynch+PRID (Group II) and PRID+PG (Group III) based on estrus response, duration of estrus, intensity of estrus, serum progesterone concentration and conception rate. The estrus response and duration of estrus after synchronization of postpartum acyclic crossbred cows inGroup I, Group II and Group III was 75.00, 100.00 and 87.50 percent; 50.62±8.39hrs, 68.00±2.61hrs and 58.63±9.36 hrs,respectively. Intensity of estrus exhibited was high of (62.5%) when synchronized with Ovsynch+PRID protocol followed by PRID+PG (50.0%) andOvsynch (25.0%) protocols. In Ovsynch (12.5% weak, 62.5% intermediate and 25% intense) Ovsynch+PRID, (0% weak, 37.5% intermediate and 62.5% intense) and PRID+PG, (12.5% weak, 37.5% intermediate and 50% intense). The mean serum progesterone concentrations in Group I, Group II and Group III on day ‘0’ were 2.56±1.04ng/ml, 1.66±0.24 ng/ml and 1.43±0.32 ng/ml,respectively and at the time of AI they were 7.60±0.87 ng/ml, 1.86±0.28 ng/ml and 2.50±0.65 ng/ml, respectively. The difference in the serum progesterone concentrations amongst all the three synchronization protocols was non-significant (P>0.05) recorded on day ‘0’ and day of AI. The first service conception rate was 50% and 50% in crossbred acyclic cows synchronized with Ovsynchand PRID+PG protocols, respectively while it was comparatively lower in Ovsynch+PRID protocol (37.50%). The overall conception rate in Ovsynch, Ovsynch+PRID and PRID+PG protocols was 50%, 50% and 62.50%. It was concluded from the present study that Ovsynch+PRID protocol obtained better estrus exhibition, while PRID+PG was found to be effective in getting optimum conception rate with fixed time artificial inseminationin postpartum acyclic crossbred cows.ensynchronization protocols; CROSSBRED COWS; estrus response; postpartumThesis