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Majid Shahmoradi

Majid SHAHMORADI1*, Fatin CEDDEN2, Hamid AMANLOU1, Ali REZAEI3 and Masoud ARABSHAHI3
Injection of hCG and GnRH after synchronization of Heatsynch and Selectsynch methods to increase the fertility of dairy cows
Abstract


A b s t r a c t:   The objectives of this study were comparison of Heatsynch (H) andα. Cows in the Hα. Following the synchronization of estrus and AI, cows were injected with either Key words: Holstein; Reproduction; Progesterone; Estradiol Selectsynch (S) synchronization methods as well as GnRH and hCG administration on 5th day after artificial insemination (AI), on plasma progesterone concentration, pregnancy rate (PR), conception rate (CR), and loss in high producing dairy cows. A total of 186 Holstein lactating cows at 35 ± 2 days postpartum were randomly assigned from a commercial herd. Cows received an injection of GnRH, followed 7 days later by PGF2 treatment group received an injection of estradiol benzoate (EB) 24 hour after the last PGF2 GnRH, hCG or saline on days 5 after AI. Blood sampling were conducted once between days 14 and 23 after AI. Pregnancy diagnoses were performed on days 45 and 90 after AI by rectal palpation. Detected in estrus (AI applied cows) and PR was higher for cows in the H treatment group than those in S treatment group. AI applied cows were 92.19 vs. 39.34% (P<0.0001), PR at 45 days were 39.68 vs. 20.66%, respectively (P<0.006). Progesterone levels on day 14 after insemination showed no significant difference between treatments but progesterone levels in pregnant and non pregnant cows 23 days after insemination, respectively, 11.43 and 1.43 ng/ml and the difference was significant (P<0.0001). GnRH or hCG treated cows 5 days after AI showed higher plasma progesterone level at 14th following AI compared to sub control group (P<0.05). Moreover, although the different was not significant, CR at 45 day after AI were found as 62.07% in GnRH, 48.39% in hCG, and 37.78 in sub control group respectively.

 

 

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