TDK conference 2024

The different methods for synchronizing the first ovulation are widespread under our circumstances. Currently the Double Ovsynch method is the method of choice for first service in dairy herds. The method is used in the negative energy balanced phase of lactation, whereas the synchronization of ovulation before the first artificial insemination leads to maximized pregnancy rates. The method was carried out in two dairy farms - with excellent, but different milk production level in Hungary. We carried out transrectal ultrasonography at the end of the involution and at early pregnancy diagnosis while confirmation of pregnancy was carried out with transrectal palpation. Our aim was to successfully apply the synchronization method and to achieve a large number of synchronized animals to evaluate the factors which may effect pregnancy success. Our data were analyzed by a computed statistical analysis software. Our retrospective clinical study was evaluating pregnancy data of 2542 dairy cows’ first service conception rate, and we also analyzed factors effecting pregnancy rate. According to pregnancy rates there was no difference between the two farms (45,8 vs. 47,8%), however the milk production rate of the study animals differed with 2000 kilograms in the standard lactation.Similarly the years of the study also did not show statistical difference (42,9 vs. 45,7 vs. 49,7%, p=0,06). Season influenced our pregnancy rate results. In summer months pregnancy rate was as low as 39%, whereas in winter months we achieved significantly better results (52,9%). Parity also showed significant effect for pregnancy rates (1. lact.:47,8%, ≥ 5. lact.:31,9%), and pregnancy losses also differed significantly according to parity (1. lakt.:7%, ≥ 5. lakt.:25%). The length of the dry off before calving also showed effect. with increased length of dry off, pregnancy rates became worse, respectively. Our results were not influenced by the days in milk where the protocol was initiated (35 DIM vs. 55 DIM). Better results were achieved when using sex sorted semen (42.2 vs. 69.0 %, p<0.001). Based on our results we are able to monitor the effect of the method on herd level reproduction parameters. The study enables us for prospective clinical evaluation in dairy herds under our circumstances.