The negative effects of cold conditions on pregnancy rates in dairy cows

Abstract

This study was conducted to determine the pregnancy rate in response to two sexual synchronization protocols in 70 healthy multiparous Fleckvieh dairy cows during the cold and warm seasons. After pairing by the actual parturition date [cold seasons (-38 to 0 ºC) (Nov - Feb) vs. warm seasons (0 to 32 ºC) (Mar-Oct)], cows were randomly subjected to either Co-Synch (CoS) or double PGF2α injection (dPG) on d 35 postpartum. Data were subjected to Chi-Square (2) analysis to determine the pregnancy rate at the first service. Overall pregnancy rates (%) at the first service were 57.1 and 40.0 for Groups CoS and dPG, respectively (2 = 2.03, P = 0.15) and 35.0 and 66.7% during cold and warm seasons, respectively (2 = 6.78, P = 0.009). The protocol effect on the pregnancy rate at the first service was insignificant during cold (2 = 1.17, P = 0.28) and warm (2 = 1.62, P = 0.20) season. In summary, the cold conditions negatively affected the pregnancy rate at the first service. The synchronization protocol methods did not differ to improve the pregnancy rate at the first service when cows were exposed to cold conditions.