The effect of different preovulatory serum estradiol concentrations on the conception rate of synchronized dairy cattle

Subject Areas : Journal of Comparative Pathobiology

قاسم اکبری ¹ , محمود بلورچی ² , پرویز هورشتی ³ , امیر نیاسری نسلجی ⁴ , پرویز تاجیک ⁵ , رحمت اکبری ⁶

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Received: 2010-11-02 Accepted : 2010-12-26 Published : 2011-08-23

Keywords: Dairy cow, proestrus, conception rate, estradiol concentration,

Abstract :

Lactating Holstein dairy cows (n = 167) were assigned randomly to four treatments groups. twogroups presynchronized with two injection of PGF2α, 14 days apart and then followed withOvsynch and Heatsynch (presynch-ovsynch or presynch-heatsynch) and two other groupspresynchronized with one injection of PGF2α and two day after that receive GnRH 6 d beforethe first GnRH injection of ovsynch and heatsynch (G6G-ovsynch or G6G-heatsynch). Fourblood samples were collected from cows for determination of plasma progesteroneconcentration. Sample 1 and 2 for determining the cyclic cows and Third samples 24h after PGFof the Ovsynch and Heatsynch protocol were taken to assay blood serum estradiol. The fourthsample was taken at 21 days afetr AI. Transrectal ultrasonography was performed to diagnosepregnant cows 30 d after AI. Mean milk production and BCS around AI time was similar amongtreatments. Estradiol concentration at proestrus was similar among groups. Although conceptionrate was higher in Presynch-Heasynch (%53 versus %43 in presynch-ovsynch and G6Gheatsynchand %39 in presynch-ovsynch) but this difference was not significance. There was asignificance positive correlation between estradiol conentration and conception rate (0.267) inour study in total but this correlation was higher in G6G-Ovsynch (0.343). This study has shownthat there is a positive corrolation between preovulatory estradiol concentation and conceptionrate in the synchronized dairy cattle.