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Year : 2015
Tome : 166
Volume : 11-12
Pages : 345-349
Title : The effect of body condition loss and milk yield on the efficiency of Ovsynch in cycling Holstein dairy cows
Authors : M. K. ESMAILI TAZANGI, A. MIRZAEI
Summary : Reproductive efficiency of dairy cows is low mainly due to reduction in conception and estrous detection. Ovsynch protocol (synchronization of ovulation) has been developed to improve the pregnancy rate in dairy farms. Therefore, the present study was performed to compare pregnancy rate using the Ovsynch protocol in lactating dairy cows with different body condition score (BCS), and to evaluate the effect of postpartum BCS loss on the pregnancy rate. One hundred and fifty five cows (primiparous, n=58 and multiparous, n=97) were assigned randomly and divided into three groups: BCS<3, BCS=3, and BCS>3 at the first GnRH injection. Cows received Ovsynch protocol (GnRH-7d-PGF2?-2d-GnRH) at diestrous stage of the estrous cycle. Cows were artificially inseminated based on the estrous detection or fixed-time insemination at 18-24 hours after second GnRH. All cows were examined by ultrasonography between 30 and 35 days after insemination for pregnancy diagnosis. Pregnancy rate was higher (P < 0.05) in multiparous cows with BCS >3 (53.8%) than that of the cows of the other BCS groups (32.4 and 16.7% in cows with BCS=3 and <3, respectively). Mean (?SD) of postpartum BCS loss from calving to first GnRH injection was lower (P<0.05) in multiparous and primiparous cows with BCS >3 (0.32 ? 0.42 and 0.33 ? 0.10) in comparison with those of the cows with BCS=3 (0.52 ? 0.39 and 0.62 ? 0.10) and cows with BCS<3 (0.78? 0.34 and 0.98 ? 0.20). The mean milk yield was significantly (P < 0.05) greater for cows with BCS > or = 3 in comparison with that of the cows with BCS < 3. In conclusion, the postpartum body condition loss is an important factor for achieving acceptable pregnancy rate after Ovsynch protocol in Holstein lactating dairy cows.
Keywords : Pregnancy rate; Ovsynch; Body condition score; Milk yield; Dairy cows
Correspondence : A. MIRZAEI
Adress : Department of Clinical Sciences, Faculty of Veterinary Medicine, Shiraz University, Shiraz, Iran. mirzaei@shirazu.ac.ir
Link : pdf

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