Endocrine Abstracts

The aim of this study was to determine of pregnancy rate when Estradiol Benzoate (EB) used in presynch method than to routine presynchronization protocol in lactating dairy cows (N: 210). In this study, cows divided in two treatment groups: control group (N: 100) and main group (N: 110). Control group cows received two injections of Cloprostenol (750 μg/Case, IM) with 14 d interval. Then, they received an injection of Gonadorelin (100 μg/Case, IM), 7 d after cloprostenol (750 μg/Case, IM) injected, followed by an injection of Gonadorelin (100 μg/Case, IM) 48 h later, finally cows artificial inseminated (AI) 16–18 h later. In main group, cows received an injection of EB (1 mg/Case, IM) instead of last injected Gonadorelin 24 h after cloprostenol injection. In main group, AI performed 48 h after EB injection. Detection of cow pregnancy performed at 42±3 d via rectal palpation. Estrus rate in control and main groups were 63 and 71%, and pregnancy rate were 44 and 41.1%, respectively. Also, pregnancy rate in estrus and non estrus cows compared in two groups that in control group were 44.4 and 43.2%, and in main group were 43.4 and 35.5%, respectively. Overall, no significant differences were detected between two synchronization methods in present study. In conclusion, Estradiol Benzoate can be use as a suitable instead to GnRH in presynch protocol.