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The objectives of the present study were to compare efficacy of Cosynch and Ovsynch estrus synchronization protocols on fertility in repeat breeder buffaloes, to study vaginal electrical resistance in various stages of estrous cycle and post insemination until pregnancy diagnosis and its relation and to estimate the biochemical constituents in cervico-vaginal mucus and its correlation with vaginal electrical resistance and pregnancy rate. A total of 24 non-descript repeat breeder buffaloes below 10 years of age were divided equally into three groups and subjected to Cosynch, Ovsynch protocols and a control group and were timely inseminated with fertile semen. Cosynch and Ovsynch protocols exhibited estrus signs (100%) within 48 to 72 h after PGF2α injection. Out of 8 repeat breeder buffaloes 3 became pregnant (37.50%) in Cosynch and 4 buffaloes became pregnant (50.00%) in Ovsynch groups respectively. In control group, out of eight repeat breeder buffaloes 2 became pregnant (25.00%) without any treatment. The VER values were lowest after 12 h from onset of estrus in all the repeat breeder buffaloes. The repeat breeder buffaloes with mean VER value of 219.26±4.64 at the time of insemination confirmed to be pregnant than compared to the non-pregnant buffaloes with mean VER values of 239.30±5.59 at the time of insemination. The VER values may be used to know the pregnancy status in buffaloes on day 8 to 9 post A.I. (317.78±13.21 vs. 309.30±12.28) in pregnant vs. non-pregnant buffaloes. The VER values rose from 317.78±13.21 on day 8 to 9 continuously up to 363.33±7.99 on day 45 in pregnant buffaloes whereas the same VER values 309.30±12.28 on day 8 declined up to 282.00±12.39 on day 45 in non-pregnant buffaloes.