Efficiency of Two Protocols of Resynchronization of Estrus and Ovulation in High-Producing Dairy Cows at Peak Lactation

Abstract The reproductive efficiency of the cows was monitored after two resynchronization protocols: Ovsynch (OVS) and Double (DOS). research initially included 70 HF who entered first synchronization protocol – Presynch. Cows that did not conceive were divided into groups introduced to protocols. In group (n=35), DOS began with application GnRH on day 22 Presynch TAI (Timed Artificial Insemination), seven days later pregnancy check-up done PGF 2α applied only non-pregnant (n=23), which remained in study. second cows, OVS started 32 animals (n=20). Progesterone (P4) concentration determined at time GnRH1, GnRH2 both then 30 Resynch TAI, ultrasound diagnosis done. A higher percentage pregnant recorded compared (45% 35%, respectively). P4 serum during measurement (GnRH1) significantly than value (p<0.05), while third (GnRH2) average conceiving lower (p<0.001) coincive. open period longer resynchronized using from protocol. conclusion, estrus dairy proved be more successful However, considering advantages OVS, it is needed determine sexual cycle best start resynchronization.