A study was carried out under field conditions on 50 acyclic/anestrus and 50 cyclic/ repeat breeder HF crossbred cows to evaluate the efficacy of four standard estrus induction/ ovulation synchronization protocols, viz., Ov_synch (GPG), Ov_synch Plus (PMSG+GPG), Double_synch (P-GPG) and Estradoublesynch (P-GPE) (10 cows in each protocol, and in untreated controls) in terms of estrus induction response and conception rates at induced estrus with fixed time AI (FTAI) and overall of 3 cycles. All

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... he selected animals received presynchronization treatment, viz., Inj. Ivermectin s.c. and Tonovita i.m. once and multimineral bolus once daily for 7 days. Repeat breeding cows received additional single shot i.m. injection of Enrofloxacin. All the anestrus and repeat breeder cows (100 %) under all four treatment protocols exhibited induced estrus between 48 and 72 hrs from PGF 2 α injection. The conception rates obtained in anestrus cows at induced estrus (FTAI) and overall of three cycles post-treatment were 20.0 and 60.0% with Ov_synch; 20.0 and 50.0% with Ov_synch Plus; 40.0 and 80.0% with Double_synch, and 30.0 and 60.0% with Estradoublesynch protocol, respectively. The corresponding conception rates in repeat breeder cows were 30.0 and 70.0% with Ov_synch; 30.0 and 50.0% with Ov_synch Plus; 40.0 and 80.0% with Double_synch, and 20.0 and 60.0% with Estradoublesynch protocol, respectively. All non-conceived repeat breeding cows under each protocol, except 1 in Ov_synch Plus protocol, continued cycling, while among 10 anestrus cows each treated with Ov_synch, Ov_synch Plus, Double_synch and Estradoublesynch protocol, 2, 2, 0 and 1 cows again turned out to be anestrus by 60 days post-induction/FTAI, respectively. Among the untreated control anestrus and repeat breeder cows (10 each), 2 and 3 cows conceived over a period of 90 days follow up giving overall conception rates of only 20.0 and 30.0%, respectively, as against the overall fertility rate of 62.5 and 65.0 % in treated anestrus and repeat breeder cows, respectively, over just mean 28-32 days of treatment, suggesting the economic utility of these protocols in handling the problem breeder cows under field conditions.