Is Doublesynch protocol a new alternative for timed artificial insemination in anestrous dairy cows

Abstract

This is the very first report that suggests high pregnancy rates can be obtained with use of the Doublesynch protocol in anestrous dairy cows. Recently, a new synchronization method has been developed (Doublesynch) that resulted in synchronized ovulations both after the first and second gonadotropin-releasing hormone (GnRH) treatments. It was suggested that this protocol has the potential to increase the pregnancy rates in primiparous dairy cows. The aim of the current study was to confirm the success of the Doublesynch protocol and further to investigate the effect of this method on pregnancy rates in anestrous cows. Lactating primiparous Holstein (Bos taurus) cows (n = 165) between 60 and 172 d postpartum were monitored twice with 10-d intervals (on Days 10 and 0) by ultrasonography, and blood samples were collected. Cows were classified as anestrous if both blood samples had progesterone (P4) concentration = 1 ng/mL. Cyclic cows were classified again as cyclic-high P4 (having an active corpus luteum) if the second blood samples had P4 concentrations >= 1 ng/mL and as cyclic-low P4 if P4 concentrations were 0.05), whereas pregnancy rates reduced dramatically as follicle size increased in the Ovsynch group, particularly in cows with follicles greater than 16 mm (45.5%, 28.1%, and 5.3%, respectively; P <0.05). Our results confirm and support observations that the Doublesynch protocol increases the pregnancy rates in postpartum primiparous cows as reported previously. Our data also demonstrate that the Doublesynch method increases the pregnancy rates in anestrous cows. Thus, these data suggest that the Doublesynch protocol can be used to obtain satisfactory pregnancy rates after TAI in both anestrous and cycling primiparous dairy cows regardless of stage of estrous cycle. (C) 2010 Elsevier Inc. All rights reserved.